pngwriter/pngwriter

C++ library for creating PNG images

pngwriter's Issues

Clang warnings

src/pngwriter.cc:

• double brackets like in if((bit_depth_ == 16))
• line 926: warning: comparison of unsigned expression < 0 is always false
  [-Wtautological-compare] if((index > 999999999)||(index < 0))

Run llvm's scan-build

cmake \
  -DCMAKE_C_COMPILER=/usr/share/clang/scan-build/ccc-analyzer \
  -DCMAKE_CXX_COMPILER=/usr/share/clang/scan-build/c++-analyzer \
  path/to/pngwriter/
scan-build make
# scan-build -enable-checker core,unix,cplusplus,alpha.cplusplus,alpha.unix,alpha.core -v [-v] make

(~25+1 bugs)

Move Some Examples To Tests

Some examples are actually tests from bug reports.
Lets move them to tests/ so users are not confused and can focus on well documented examples.

Add include/pngwriter.h to install

Install the pngwriter.h file to include/

Better Mac Support: RPath

Add RPATH, see kitware blog & kitware wiki and warning:

Make Warning (dev):
  Policy CMP0042 is not set: MACOSX_RPATH is enabled by default.  Run "cmake
  --help-policy CMP0042" for policy details.  Use the cmake_policy command to
  set the policy and suppress this warning.

  MACOSX_RPATH is not specified for the following targets:

   pngwriter

This warning is for project developers.  Use -Wno-dev to suppress it.

thx to @PrometheusPi for spotting that.

Careful:

• will need cmake 2.8.12+
• is bad for some linux'es: debian policy

Ref

• better docu in the cmake wiki

Reduce Code Redundancy

The functions pngwriter::bezier and pngwriter::bezier_blend are one example. the only difference in their 10+ lines body are line vs. line_blend. I think this is not the only case I saw.

pngwriter::plot_text_utf8, pngwriter::get_text_width_utf8 and pngwriter::plot_text_utf8_blend is another triple contender with an even larger body of copy-paste.

How do I find these doubles? I'm trying out cppcheck, see #75

[../src/pngwriter.cc:753]: (style) The scope of the variable 'temp1' can be reduced.
[../src/pngwriter.cc:753]: (style) The scope of the variable 'temp2' can be reduced.
[../src/pngwriter.cc:820]: (style) The scope of the variable 'temp1' can be reduced.
[../src/pngwriter.cc:820]: (style) The scope of the variable 'temp2' can be reduced.
[../src/pngwriter.cc:820]: (style) The scope of the variable 'temp3' can be reduced.
[../src/pngwriter.cc:820]: (style) The scope of the variable 'temp4' can be reduced.
[../src/pngwriter.cc:820]: (style) The scope of the variable 'temp5' can be reduced.
[../src/pngwriter.cc:1972]: (style) The scope of the variable 'newx' can be reduced.
[../src/pngwriter.cc:1972]: (style) The scope of the variable 'newy' can be reduced.
[../src/pngwriter.cc:2174]: (style) The scope of the variable 'z' can be reduced.
[../src/pngwriter.cc:2546]: (style) The scope of the variable 'z' can be reduced.
[../src/pngwriter.cc:3758]: (style) The scope of the variable 'newx' can be reduced.
[../src/pngwriter.cc:3758]: (style) The scope of the variable 'newy' can be reduced.
[../src/pngwriter.cc:3944]: (style) The scope of the variable 'z' can be reduced.

Valgrind the examples for memory leaks

Check for memory leaks.

Pngwriter seems to read files wrong

I have these two images (I hope they aren't changed by uploading it (happened to me at least on sourceforge already))

The second one was sent through gimp without changing it. One notable difference seems to be the bit depth which is 8 bits per channel for b.png instead of 16 bits as the first image has.

I check if they are identical with python:

#!/usr/bin/python
# python oI_300x200.png oI_300x200-gimp.png

from numpy import *
from matplotlib.pyplot import *
from mpl_toolkits.mplot3d import Axes3D
from PIL import Image
import sys  # argv

diff = array( Image.open( sys.argv[1] ) ) - array( Image.open( sys.argv[2] ) )
print "diff.sum =",diff.sum()

fig = figure()
imshow( diff )
tight_layout()
show()

which returns:

diff.sum = 0

And I also check if they are identical with pngwriter in C++:

/*
file=comparePng; g++ -c -std=c++11 -Wall -Wextra -DNO_FREETYPE -I$PNGWRITER_ROOT/include -o $file.o $file.cpp; g++ -L$PNGWRITER_ROOT/lib ./$file.o -Wl,-Bstatic -lpngwriter -lpng -lfreetype -lz -Wl,-Bdynamic -o $file.exe; ./$file.exe ../buildwoalpaka/oI_1200x1000.png-diffraction.png ../buildwoalpaka/oI_1200x1000-diffraction-center-white-out.png
*/

#include <iostream>
#include <iomanip>
#include <cmath>
#include <cassert>
#include <pngwriter.h>


int main( int argc, char ** argv )
{
    assert( argc >= 3 );
    auto & fnameA = argv[1];
    auto & fnameB = argv[2];
    int Nx, Ny;

    int * diff = NULL;
    pngwriter png( 1, 1, 0, "a" );
    png.pngwriter_rename("b");
    char test[25] = "a";
    png.pngwriter_rename( test );
    std::cout << "read in " << fnameA;
    {
        png.readfromfile( fnameA );
        std::cout << " (bit depth = " << png.getbitdepth() << ")" << std::endl;

        Nx = png.getwidth( );
        Ny = png.getheight( );

        diff = new int[ Nx*Ny ];
        for ( int iy = 0; iy < Ny; ++iy )
        {
            for ( int ix = 0; ix < Nx; ++ix )
            {
                int const i = (iy*Nx)+ix;
                diff[ (iy*Nx)+ix ] = png.read( 1+ix, 1+iy, 1 );
                if ( i < 5 or ( i > Nx*Ny/2+Nx/2 and i < Nx*Ny/2+Nx/2+5 ) )
                    std::cout << "[i=" << std::setw(6) << i << "] : "
                              << diff[i] << std::endl;
                assert( png.read( 1+ix, 1+iy, 1 ) == png.read( 1+ix, 1+iy, 2 ) &&
                        "red channel must be equal to blue channel" );
                assert( png.read( 1+ix, 1+iy, 2 ) == png.read( 1+ix, 1+iy, 3 ) &&
                        "blue channel must be equal to green channel" );
            }
        }
    }
    std::cout << "subtract " << fnameB;
    {
        png.readfromfile( fnameB );
        std::cout << " (bit depth = " << png.getbitdepth() << ")" << std::endl;

        assert( Nx == png.getwidth( ) );
        assert( Ny == png.getheight( ) );

        for ( int iy = 0; iy < Ny; ++iy )
        {
            for ( int ix = 0; ix < Nx; ++ix )
            {
                int const i = (iy*Nx)+ix;
                diff[i] -= png.read( 1+ix, 1+iy, 1 );
                if ( i < 5 or ( i > Nx*Ny/2+Nx/2 and i < Nx*Ny/2+Nx/2+5 ) )
                    std::cout << "[i=" << std::setw(6) << i << "] : "
                              << png.read( 1+ix, 1+iy, 1 ) << std::endl;
                assert( png.read( 1+ix, 1+iy, 1 ) == png.read( 1+ix, 1+iy, 2 ) &&
                        "red channel must be equal to blue channel" );
                assert( png.read( 1+ix, 1+iy, 2 ) == png.read( 1+ix, 1+iy, 3 ) &&
                        "blue channel must be equal to green channel" );
            }
        }
    }
    std::cout << "Difference:" << std::endl;
    int diffAbsSum = 0, maxDiff = 0, minDiff = 0;
    for ( int i = 0; i < Nx*Ny; ++i )
    {
        if ( diff[i] != 0 and ( i < 5 or ( i > Nx*Ny/2+Nx/2 and i < Nx*Ny/2+Nx/2+5 ) ) )
            std::cout << "[i=" << std::setw(6) << i << "] " << diff[i] << std::endl;
        diffAbsSum += std::abs( diff[i] );
        maxDiff = std::max( maxDiff, diff[i] );
        minDiff = std::min( minDiff, diff[i] );
    }
    std::cout << "minimum difference : " << minDiff << std::endl;
    std::cout << "maximum difference : " << maxDiff << std::endl;

    return 0;
}

which returns

read in a.png (bit depth = 16)
[i=     0] : 19
[i=     1] : 16
[i=     2] : 5
[i=     3] : 8
[i=     4] : 15
[i=600601] : 40630
[i=600602] : 18786
[i=600603] : 10525
[i=600604] : 4403
subtract b.png (bit depth = 8)
[i=     0] : 0
[i=     1] : 0
[i=     2] : 0
[i=     3] : 0
[i=     4] : 0
[i=600601] : 40448
[i=600602] : 18688
[i=600603] : 10496
[i=600604] : 4352
Difference:
[i=     0] 19
[i=     1] 16
[i=     2] 5
[i=     3] 8
[i=     4] 15
[i=600601] 182
[i=600602] 98
[i=600603] 29
[i=600604] 51
minimum difference : 0
maximum difference : 255

With pull request #90 applied the output is:

read in a.png (bit depth = 16)
[i=     0] : 19
[i=     1] : 16
[i=     2] : 5
[i=     3] : 8
[i=     4] : 15
[i=600601] : 40630
[i=600602] : 18786
[i=600603] : 10525
[i=600604] : 4403
subtract b.png (bit depth = 8)
[i=     0] : 0
[i=     1] : 0
[i=     2] : 0
[i=     3] : 0
[i=     4] : 0
[i=600601] : 40606
[i=600602] : 18761
[i=600603] : 10537
[i=600604] : 4369
Difference:
[i=     0] 19
[i=     1] 16
[i=     2] 5
[i=     3] 8
[i=     4] 15
[i=600601] 24
[i=600602] 25
[i=600603] -12
[i=600604] 34
minimum difference : -53
maximum difference : 255

I'm not entirely sure why. And why this doesn't happen with python. Here are the outputs by ImageMagick's identify

identify -verbose a.png
Image: a.png
  Format: PNG (Portable Network Graphics)
  Mime type: image/png
  Class: DirectClass
  Geometry: 1200x1000+0+0
  Units: Undefined
  Type: Grayscale
  Endianess: Undefined
  Colorspace: Gray
  Depth: 16-bit
  Channel depth:
    gray: 16-bit
  Channel statistics:
    Pixels: 1200000
    Gray:
      min: 0 (0)
      max: 65535 (1)
      mean: 13.0979 (0.000199862)
      standard deviation: 160.475 (0.0024487)
      kurtosis: 57702.6
      skewness: 201.147
  Rendering intent: Perceptual
  Gamma: 0.6
  Chromaticity:
    red primary: (0.64,0.33)
    green primary: (0.3,0.6)
    blue primary: (0.15,0.06)
    white point: (0.3127,0.329)
  Background color: gray(255)
  Border color: gray(223)
  Matte color: gray(189)
  Transparent color: gray(0)
  Interlace: None
  Intensity: Undefined
  Compose: Over
  Page geometry: 1200x1000+0+0
  Dispose: Undefined
  Iterations: 0
  Compression: Zip
  Orientation: Undefined
  Properties:
    Author: PNGwriter Author: Paul Blackburn
    Creation Time: 5 Mar 2016 22:01:06 +0000
    date:create: 2016-03-06T01:44:38+01:00
    date:modify: 2016-03-05T23:01:07+01:00
    Description: http://pngwriter.sourceforge.net/
    png:gAMA: gamma=0.60000002 (See Gamma, above)
    png:IHDR.bit-depth-orig: 16
    png:IHDR.bit_depth: 16
    png:IHDR.color-type-orig: 2
    png:IHDR.color_type: 2 (Truecolor)
    png:IHDR.interlace_method: 0 (Not interlaced)
    png:IHDR.width,height: 1200, 1000
    png:text: 5 tEXt/zTXt/iTXt chunks were found
    png:tIME: 2016-03-05T22:01:06Z
    signature: c904ab0fdffc555f82c8ff652676f6490812fdc17dc3ae4d8e201067436abba2
    Software: PNGwriter: An easy to use graphics library.
    Title: oI_1200x1000.png-diffraction.png
  Artifacts:
    filename: a.png
    verbose: true
  Tainted: False
  Filesize: 1.234MB
  Number pixels: 1.2M
  Pixels per second: 20MB
  User time: 0.060u
  Elapsed time: 0:01.059
  Version: ImageMagick 6.8.9-9 Q16 x86_64 2016-02-02 http://www.imagemagick.org

and for file b.png

identify -verbose b.png
Image: b.png
  Format: PNG (Portable Network Graphics)
  Mime type: image/png
  Class: DirectClass
  Geometry: 1200x1000+0+0
  Resolution: 28.35x28.35
  Print size: 42.328x35.2734
  Units: PixelsPerCentimeter
  Type: Grayscale
  Endianess: Undefined
  Colorspace: Gray
  Depth: 8-bit
  Channel depth:
    gray: 8-bit
  Channel statistics:
    Pixels: 1200000
    Gray:
      min: 0 (0)
      max: 255 (1)
      mean: 0.0108958 (4.27288e-05)
      standard deviation: 0.615423 (0.00241342)
      kurtosis: 61157.9
      skewness: 209.611
  Colors: 55
  Histogram:
   1196167: (  0,  0,  0) #000000 gray(0)
      2264: (  1,  1,  1) #010101 gray(1)
       628: (  2,  2,  2) #020202 gray(2)
       284: (  3,  3,  3) #030303 gray(3)
       172: (  4,  4,  4) #040404 gray(4)
       102: (  5,  5,  5) #050505 gray(5)
        56: (  6,  6,  6) #060606 gray(6)
        34: (  7,  7,  7) #070707 gray(7)
        44: (  8,  8,  8) #080808 gray(8)
        30: (  9,  9,  9) #090909 gray(9)
        20: ( 10, 10, 10) #0A0A0A gray(10)
        28: ( 11, 11, 11) #0B0B0B gray(11)
        22: ( 12, 12, 12) #0C0C0C gray(12)
         6: ( 13, 13, 13) #0D0D0D gray(13)
        12: ( 14, 14, 14) #0E0E0E gray(14)
        10: ( 15, 15, 15) #0F0F0F gray(15)
        10: ( 16, 16, 16) #101010 gray(16)
         8: ( 17, 17, 17) #111111 gray(17)
        10: ( 18, 18, 18) #121212 gray(18)
         4: ( 19, 19, 19) #131313 gray(19)
         2: ( 20, 20, 20) #141414 gray(20)
         2: ( 21, 21, 21) #151515 gray(21)
         6: ( 22, 22, 22) #161616 gray(22)
         4: ( 23, 23, 23) #171717 gray(23)
         4: ( 25, 25, 25) #191919 gray(25)
         4: ( 26, 26, 26) #1A1A1A gray(26)
         2: ( 27, 27, 27) #1B1B1B gray(27)
         4: ( 28, 28, 28) #1C1C1C gray(28)
         6: ( 30, 30, 30) #1E1E1E gray(30)
         2: ( 31, 31, 31) #1F1F1F gray(31)
         2: ( 32, 32, 32) #202020 gray(32)
         2: ( 33, 33, 33) #212121 gray(33)
         2: ( 34, 34, 34) #222222 gray(34)
         4: ( 35, 35, 35) #232323 gray(35)
         4: ( 36, 36, 36) #242424 gray(36)
         2: ( 37, 37, 37) #252525 gray(37)
         2: ( 39, 39, 39) #272727 gray(39)
         2: ( 41, 41, 41) #292929 gray(41)
         2: ( 42, 42, 42) #2A2A2A gray(42)
         2: ( 44, 44, 44) #2C2C2C gray(44)
         2: ( 49, 49, 49) #313131 gray(49)
         2: ( 51, 51, 51) #333333 gray(51)
         2: ( 54, 54, 54) #363636 gray(54)
         2: ( 57, 57, 57) #393939 gray(57)
         2: ( 59, 59, 59) #3B3B3B gray(59)
         2: ( 60, 60, 60) #3C3C3C gray(60)
         2: ( 69, 69, 69) #454545 gray(69)
         2: ( 73, 73, 73) #494949 gray(73)
         2: ( 83, 83, 83) #535353 gray(83)
         2: ( 94, 94, 94) #5E5E5E gray(94)
         2: ( 96, 96, 96) #606060 gray(96)
         2: (158,158,158) #9E9E9E gray(158)
         2: (169,169,169) #A9A9A9 gray(169)
         2: (192,192,192) #C0C0C0 gray(192)
         1: (255,255,255) #FFFFFF gray(255)
  Rendering intent: Perceptual
  Gamma: 0.454545
  Chromaticity:
    red primary: (0.64,0.33)
    green primary: (0.3,0.6)
    blue primary: (0.15,0.06)
    white point: (0.3127,0.329)
  Background color: gray(255)
  Border color: gray(223)
  Matte color: gray(189)
  Transparent color: gray(0)
  Interlace: None
  Intensity: Undefined
  Compose: Over
  Page geometry: 1200x1000+0+0
  Dispose: Undefined
  Iterations: 0
  Compression: Zip
  Orientation: Undefined
  Properties:
    date:create: 2016-03-06T01:44:40+01:00
    date:modify: 2016-03-05T23:08:51+01:00
    png:IHDR.bit-depth-orig: 8
    png:IHDR.bit_depth: 8
    png:IHDR.color-type-orig: 2
    png:IHDR.color_type: 2 (Truecolor)
    png:IHDR.interlace_method: 0 (Not interlaced)
    png:IHDR.width,height: 1200, 1000
    png:pHYs: x_res=2835, y_res=2835, units=1
    png:sRGB: intent=0 (Perceptual Intent)
    png:tIME: 2016-03-05T22:08:51Z
    signature: f1e466877cb0fedd6e4c940f801b4db5085c8c4b7c36277327d2b93e2794cb95
  Artifacts:
    filename: b.png
    verbose: true
  Tainted: False
  Filesize: 10.1KB
  Number pixels: 1.2M
  Pixels per second: 40MB
  User time: 0.020u
  Elapsed time: 0:01.029
  Version: ImageMagick 6.8.9-9 Q16 x86_64 2016-02-02 http://www.imagemagick.org

and lastly the diff for easier viewing:

colordiff <(identify -verbose a.png) <(identify -verbose b.png)
1c1
< Image: a.png

---
> Image: b.png
6c6,8
<   Units: Undefined

---
>   Resolution: 28.35x28.35
>   Print size: 42.328x35.2734
>   Units: PixelsPerCentimeter
10c12
<   Depth: 16-bit

---
>   Depth: 8-bit
12c14
<     gray: 16-bit

---
>     gray: 8-bit
17,21c19,80
<       max: 65535 (1)
<       mean: 13.0979 (0.000199862)
<       standard deviation: 160.475 (0.0024487)
<       kurtosis: 57702.6
<       skewness: 201.147

---
>       max: 255 (1)
>       mean: 0.0108958 (4.27288e-05)
>       standard deviation: 0.615423 (0.00241342)
>       kurtosis: 61157.9
>       skewness: 209.611
>   Colors: 55
>   Histogram:
>    1196167: (  0,  0,  0) #000000 gray(0)
>       2264: (  1,  1,  1) #010101 gray(1)
>        628: (  2,  2,  2) #020202 gray(2)
>        284: (  3,  3,  3) #030303 gray(3)
>        172: (  4,  4,  4) #040404 gray(4)
>        102: (  5,  5,  5) #050505 gray(5)
>         56: (  6,  6,  6) #060606 gray(6)
>         34: (  7,  7,  7) #070707 gray(7)
>         44: (  8,  8,  8) #080808 gray(8)
>         30: (  9,  9,  9) #090909 gray(9)
>         20: ( 10, 10, 10) #0A0A0A gray(10)
>         28: ( 11, 11, 11) #0B0B0B gray(11)
>         22: ( 12, 12, 12) #0C0C0C gray(12)
>          6: ( 13, 13, 13) #0D0D0D gray(13)
>         12: ( 14, 14, 14) #0E0E0E gray(14)
>         10: ( 15, 15, 15) #0F0F0F gray(15)
>         10: ( 16, 16, 16) #101010 gray(16)
>          8: ( 17, 17, 17) #111111 gray(17)
>         10: ( 18, 18, 18) #121212 gray(18)
>          4: ( 19, 19, 19) #131313 gray(19)
>          2: ( 20, 20, 20) #141414 gray(20)
>          2: ( 21, 21, 21) #151515 gray(21)
>          6: ( 22, 22, 22) #161616 gray(22)
>          4: ( 23, 23, 23) #171717 gray(23)
>          4: ( 25, 25, 25) #191919 gray(25)
>          4: ( 26, 26, 26) #1A1A1A gray(26)
>          2: ( 27, 27, 27) #1B1B1B gray(27)
>          4: ( 28, 28, 28) #1C1C1C gray(28)
>          6: ( 30, 30, 30) #1E1E1E gray(30)
>          2: ( 31, 31, 31) #1F1F1F gray(31)
>          2: ( 32, 32, 32) #202020 gray(32)
>          2: ( 33, 33, 33) #212121 gray(33)
>          2: ( 34, 34, 34) #222222 gray(34)
>          4: ( 35, 35, 35) #232323 gray(35)
>          4: ( 36, 36, 36) #242424 gray(36)
>          2: ( 37, 37, 37) #252525 gray(37)
>          2: ( 39, 39, 39) #272727 gray(39)
>          2: ( 41, 41, 41) #292929 gray(41)
>          2: ( 42, 42, 42) #2A2A2A gray(42)
>          2: ( 44, 44, 44) #2C2C2C gray(44)
>          2: ( 49, 49, 49) #313131 gray(49)
>          2: ( 51, 51, 51) #333333 gray(51)
>          2: ( 54, 54, 54) #363636 gray(54)
>          2: ( 57, 57, 57) #393939 gray(57)
>          2: ( 59, 59, 59) #3B3B3B gray(59)
>          2: ( 60, 60, 60) #3C3C3C gray(60)
>          2: ( 69, 69, 69) #454545 gray(69)
>          2: ( 73, 73, 73) #494949 gray(73)
>          2: ( 83, 83, 83) #535353 gray(83)
>          2: ( 94, 94, 94) #5E5E5E gray(94)
>          2: ( 96, 96, 96) #606060 gray(96)
>          2: (158,158,158) #9E9E9E gray(158)
>          2: (169,169,169) #A9A9A9 gray(169)
>          2: (192,192,192) #C0C0C0 gray(192)
>          1: (255,255,255) #FFFFFF gray(255)
23c82
<   Gamma: 0.6

---
>   Gamma: 0.454545
42,49c101,104
<     Author: PNGwriter Author: Paul Blackburn
<     Creation Time: 5 Mar 2016 22:01:06 +0000
<     date:create: 2016-03-06T01:44:38+01:00
<     date:modify: 2016-03-05T23:01:07+01:00
<     Description: http://pngwriter.sourceforge.net/
<     png:gAMA: gamma=0.60000002 (See Gamma, above)
<     png:IHDR.bit-depth-orig: 16
<     png:IHDR.bit_depth: 16

---
>     date:create: 2016-03-06T01:44:40+01:00
>     date:modify: 2016-03-05T23:08:51+01:00
>     png:IHDR.bit-depth-orig: 8
>     png:IHDR.bit_depth: 8
54,58c109,112
<     png:text: 5 tEXt/zTXt/iTXt chunks were found
<     png:tIME: 2016-03-05T22:01:06Z
<     signature: c904ab0fdffc555f82c8ff652676f6490812fdc17dc3ae4d8e201067436abba2
<     Software: PNGwriter: An easy to use graphics library.
<     Title: oI_1200x1000.png-diffraction.png

---
>     png:pHYs: x_res=2835, y_res=2835, units=1
>     png:sRGB: intent=0 (Perceptual Intent)
>     png:tIME: 2016-03-05T22:08:51Z
>     signature: f1e466877cb0fedd6e4c940f801b4db5085c8c4b7c36277327d2b93e2794cb95
60c114
<     filename: a.png

---
>     filename: b.png
63c117
<   Filesize: 1.234MB

---
>   Filesize: 10.1KB
65,67c119,121
<   Pixels per second: 15MB
<   User time: 0.060u
<   Elapsed time: 0:01.079

---
>   Pixels per second: 40MB
>   User time: 0.020u
>   Elapsed time: 0:01.030

So the 3 in my opinion main differences are:

• bit depth in a is 16-bit, b 8-bit
• file size, mainly because of bit depth I guess, but maybe also stronger compression?
• gamma! is either 0.6 in a.png or 0.454545 in b.png, but this difference is so large, this doesn't explain, why the resulting pixel differences are at maximum 255, i.e. 8 bit

Lastly!
The 16-bit version returns non-zero values for i=0...5, although they should be perfectly 0!

Check includes for std libs

Some standard lib includes are a bit adventurous.

E.g. the correct std-lib math include in c++ should look:

#include <cmath>

also check:

• include explicitly libm/m in CMakeLists.txt

Write CMake Module

Write a CMake Module like in ComputationalRadiationPhysics/libSplash#78

8 Bit Reads: Upper Bound Broken of Scale-Up to 16-bit

As 0.996109 ~ 1-1/255 this seems to happen because of some error in upscaling 255 to 65535. So unlike mentioned in the documentation

returned value will be of type int and be between 0 and 65535.

the highest value is not 65535 but 65280=65535-255.
This bug afflicts both read and dread and all other read functions which call read, like scaling and interpolation, ....
I will submit a pull request shortly.

Correct Compiler Warnings

Remove Compiler Warnings:

pngwriter/src/pngwriter.cc`: in »void pngwriter::close()«:
pngwriter/src/pngwriter.cc:991:22: ... »png_charp {aka char_}« [-Wwrite-strings]
pngwriter/src/pngwriter.cc:994:22: ... »png_charp {aka char_}« [-Wwrite-strings]
pngwriter/src/pngwriter.cc:997:22: ... »png_charp {aka char_}« [-Wwrite-strings]
pngwriter/src/pngwriter.cc:1000:22: ... »png_charp {aka char_}« [-Wwrite-strings]
pngwriter/src/pngwriter.cc:1003:22: ... »png_charp {aka char*}« [-Wwrite-strings]

See here.

Add Packing Routines

Add CPack Routines like ComputationalRadiationPhysics/libSplash#82

or via https://github.com/jordansissel/fpm

cannot plot text

Hi,
I write the short test, it only generates a full black png.

int main()
{
   pngwriter one(300,300,0,"mytest.png");   
   std::cout << "Generating mytest.png...";
   one.plot_text("Ubuntu-M.ttf", 16, 30, 30,0, "Hello World", 255,255,255);
   one.write_png();
   return 0;
}

Makefile still references the old, top-level README file

See https://github.com/ax3l/pngwriter/blob/release-0.5.5/Makefile#L126-L146

CMake: build tests/ folder

Add the tests/ dir to CMake as soon as #26 is merged.

Rebuild Internal Storage

It might be worth re-building the internal image storage in a separate class.
That should make support for issues like #15 way easier.

Compile Examples

Add examples/ to CMakeLists.txt.

Add "const" Interfaces

Add "const" methods to all pngwriter:: methods that do not change the state of the object.

Feature request/submission from Alex Flint (Dec 12th, 2006).

Unused Parameters

GCC 4.8.5 prints the following warnings with release 0.5.6 (on missing Freetype support):

src/pngwriter.cc:2730:6: warning: unused parameter ‘face_path’ [-Wunused-parameter]
 void pngwriter::plot_text( char * face_path, int fontsize, int x_start, int y_start, double angle, char * text, int red, int green, int blue)
      ^
src/pngwriter.cc:2730:6: warning: unused parameter ‘fontsize’ [-Wunused-parameter]
src/pngwriter.cc:2730:6: warning: unused parameter ‘x_start’ [-Wunused-parameter]
src/pngwriter.cc:2730:6: warning: unused parameter ‘y_start’ [-Wunused-parameter]
src/pngwriter.cc:2730:6: warning: unused parameter ‘angle’ [-Wunused-parameter]
src/pngwriter.cc:2730:6: warning: unused parameter ‘text’ [-Wunused-parameter]
src/pngwriter.cc:2730:6: warning: unused parameter ‘red’ [-Wunused-parameter]
src/pngwriter.cc:2730:6: warning: unused parameter ‘green’ [-Wunused-parameter]
src/pngwriter.cc:2730:6: warning: unused parameter ‘blue’ [-Wunused-parameter]
src/pngwriter.cc:2736:6: warning: unused parameter ‘face_path’ [-Wunused-parameter]
 void pngwriter::plot_text( char * face_path, int fontsize, int x_start, int y_start, double angle, char * text, double red, double green, double blue)
      ^
src/pngwriter.cc:2736:6: warning: unused parameter ‘fontsize’ [-Wunused-parameter]
src/pngwriter.cc:2736:6: warning: unused parameter ‘x_start’ [-Wunused-parameter]
src/pngwriter.cc:2736:6: warning: unused parameter ‘y_start’ [-Wunused-parameter]
src/pngwriter.cc:2736:6: warning: unused parameter ‘angle’ [-Wunused-parameter]
src/pngwriter.cc:2736:6: warning: unused parameter ‘text’ [-Wunused-parameter]
src/pngwriter.cc:2736:6: warning: unused parameter ‘red’ [-Wunused-parameter]
src/pngwriter.cc:2736:6: warning: unused parameter ‘green’ [-Wunused-parameter]
src/pngwriter.cc:2736:6: warning: unused parameter ‘blue’ [-Wunused-parameter]
src/pngwriter.cc:2743:6: warning: unused parameter ‘face_path’ [-Wunused-parameter]
 void pngwriter::plot_text_utf8( char * face_path, int fontsize, int x_start, int y_start, double angle, char * text, int red, int green, int blue)
      ^
src/pngwriter.cc:2743:6: warning: unused parameter ‘fontsize’ [-Wunused-parameter]
src/pngwriter.cc:2743:6: warning: unused parameter ‘x_start’ [-Wunused-parameter]
src/pngwriter.cc:2743:6: warning: unused parameter ‘y_start’ [-Wunused-parameter]
src/pngwriter.cc:2743:6: warning: unused parameter ‘angle’ [-Wunused-parameter]
src/pngwriter.cc:2743:6: warning: unused parameter ‘text’ [-Wunused-parameter]
src/pngwriter.cc:2743:6: warning: unused parameter ‘red’ [-Wunused-parameter]
src/pngwriter.cc:2743:6: warning: unused parameter ‘green’ [-Wunused-parameter]
src/pngwriter.cc:2743:6: warning: unused parameter ‘blue’ [-Wunused-parameter]
src/pngwriter.cc:2730:6: warning: unused parameter ‘face_path’ [-Wunused-parameter]
 void pngwriter::plot_text( char * face_path, int fontsize, int x_start, int y_start, double angle, char * text, int red, int green, int blue)
      ^
src/pngwriter.cc:2730:6: warning: unused parameter ‘fontsize’ [-Wunused-parameter]
src/pngwriter.cc:2730:6: warning: unused parameter ‘x_start’ [-Wunused-parameter]
src/pngwriter.cc:2730:6: warning: unused parameter ‘y_start’ [-Wunused-parameter]
src/pngwriter.cc:2730:6: warning: unused parameter ‘angle’ [-Wunused-parameter]
src/pngwriter.cc:2730:6: warning: unused parameter ‘text’ [-Wunused-parameter]
src/pngwriter.cc:2730:6: warning: unused parameter ‘red’ [-Wunused-parameter]
src/pngwriter.cc:2730:6: warning: unused parameter ‘green’ [-Wunused-parameter]
src/pngwriter.cc:2730:6: warning: unused parameter ‘blue’ [-Wunused-parameter]
src/pngwriter.cc:2749:6: warning: unused parameter ‘face_path’ [-Wunused-parameter]
 void pngwriter::plot_text_utf8( char * face_path, int fontsize, int x_start, int y_start, double angle, char * text, double red, double green, double blue)
      ^
src/pngwriter.cc:2749:6: warning: unused parameter ‘fontsize’ [-Wunused-parameter]
src/pngwriter.cc:2749:6: warning: unused parameter ‘x_start’ [-Wunused-parameter]
src/pngwriter.cc:2749:6: warning: unused parameter ‘y_start’ [-Wunused-parameter]
src/pngwriter.cc:2749:6: warning: unused parameter ‘angle’ [-Wunused-parameter]
src/pngwriter.cc:2749:6: warning: unused parameter ‘text’ [-Wunused-parameter]
src/pngwriter.cc:2749:6: warning: unused parameter ‘red’ [-Wunused-parameter]
src/pngwriter.cc:2749:6: warning: unused parameter ‘green’ [-Wunused-parameter]
src/pngwriter.cc:2749:6: warning: unused parameter ‘blue’ [-Wunused-parameter]
src/pngwriter.cc:2736:6: warning: unused parameter ‘face_path’ [-Wunused-parameter]
 void pngwriter::plot_text( char * face_path, int fontsize, int x_start, int y_start, double angle, char * text, double red, double green, double blue)
      ^
src/pngwriter.cc:2736:6: warning: unused parameter ‘fontsize’ [-Wunused-parameter]
src/pngwriter.cc:2736:6: warning: unused parameter ‘x_start’ [-Wunused-parameter]
src/pngwriter.cc:2736:6: warning: unused parameter ‘y_start’ [-Wunused-parameter]
src/pngwriter.cc:2736:6: warning: unused parameter ‘angle’ [-Wunused-parameter]
src/pngwriter.cc:2736:6: warning: unused parameter ‘text’ [-Wunused-parameter]
src/pngwriter.cc:2736:6: warning: unused parameter ‘red’ [-Wunused-parameter]
src/pngwriter.cc:2736:6: warning: unused parameter ‘green’ [-Wunused-parameter]
src/pngwriter.cc:2736:6: warning: unused parameter ‘blue’ [-Wunused-parameter]
src/pngwriter.cc:2756:5: warning: unused parameter ‘face_path’ [-Wunused-parameter]
 int pngwriter::get_text_width(char * face_path, int fontsize, char * text)
     ^
src/pngwriter.cc:2756:5: warning: unused parameter ‘fontsize’ [-Wunused-parameter]
src/pngwriter.cc:2756:5: warning: unused parameter ‘text’ [-Wunused-parameter]
src/pngwriter.cc:2743:6: warning: unused parameter ‘face_path’ [-Wunused-parameter]
 void pngwriter::plot_text_utf8( char * face_path, int fontsize, int x_start, int y_start, double angle, char * text, int red, int green, int blue)
      ^
src/pngwriter.cc:2743:6: warning: unused parameter ‘fontsize’ [-Wunused-parameter]
src/pngwriter.cc:2743:6: warning: unused parameter ‘x_start’ [-Wunused-parameter]
src/pngwriter.cc:2743:6: warning: unused parameter ‘y_start’ [-Wunused-parameter]
src/pngwriter.cc:2743:6: warning: unused parameter ‘angle’ [-Wunused-parameter]
src/pngwriter.cc:2743:6: warning: unused parameter ‘text’ [-Wunused-parameter]
src/pngwriter.cc:2763:5: warning: unused parameter ‘face_path’ [-Wunused-parameter]
 int pngwriter::get_text_width_utf8(char * face_path, int fontsize,  char * text)
     ^
src/pngwriter.cc:2743:6: warning: unused parameter ‘red’ [-Wunused-parameter]
src/pngwriter.cc:2743:6: warning: unused parameter ‘green’ [-Wunused-parameter]
src/pngwriter.cc:2743:6: warning: unused parameter ‘blue’ [-Wunused-parameter]
src/pngwriter.cc:2763:5: warning: unused parameter ‘fontsize’ [-Wunused-parameter]
src/pngwriter.cc:2763:5: warning: unused parameter ‘text’ [-Wunused-parameter]
src/pngwriter.cc:2749:6: warning: unused parameter ‘face_path’ [-Wunused-parameter]
 void pngwriter::plot_text_utf8( char * face_path, int fontsize, int x_start, int y_start, double angle, char * text, double red, double green, double blue)
      ^
src/pngwriter.cc:2749:6: warning: unused parameter ‘fontsize’ [-Wunused-parameter]
src/pngwriter.cc:2749:6: warning: unused parameter ‘x_start’ [-Wunused-parameter]
src/pngwriter.cc:2749:6: warning: unused parameter ‘y_start’ [-Wunused-parameter]
src/pngwriter.cc:2749:6: warning: unused parameter ‘angle’ [-Wunused-parameter]
src/pngwriter.cc:2749:6: warning: unused parameter ‘text’ [-Wunused-parameter]
src/pngwriter.cc:2749:6: warning: unused parameter ‘red’ [-Wunused-parameter]
src/pngwriter.cc:2749:6: warning: unused parameter ‘green’ [-Wunused-parameter]
src/pngwriter.cc:2749:6: warning: unused parameter ‘blue’ [-Wunused-parameter]
src/pngwriter.cc:2756:5: warning: unused parameter ‘face_path’ [-Wunused-parameter]
 int pngwriter::get_text_width(char * face_path, int fontsize, char * text)
     ^
src/pngwriter.cc:2756:5: warning: unused parameter ‘fontsize’ [-Wunused-parameter]
src/pngwriter.cc:2756:5: warning: unused parameter ‘text’ [-Wunused-parameter]
src/pngwriter.cc:2763:5: warning: unused parameter ‘face_path’ [-Wunused-parameter]
 int pngwriter::get_text_width_utf8(char * face_path, int fontsize,  char * text)
     ^
src/pngwriter.cc:2763:5: warning: unused parameter ‘fontsize’ [-Wunused-parameter]
src/pngwriter.cc:2763:5: warning: unused parameter ‘text’ [-Wunused-parameter]
src/pngwriter.cc:4159:6: warning: unused parameter ‘face_path’ [-Wunused-parameter]
 void pngwriter::plot_text_blend( char * face_path, int fontsize, int x_start, int y_start, double angle, char * text, double opacity, int red, int green, int blue)
      ^
src/pngwriter.cc:4159:6: warning: unused parameter ‘fontsize’ [-Wunused-parameter]
src/pngwriter.cc:4159:6: warning: unused parameter ‘x_start’ [-Wunused-parameter]
src/pngwriter.cc:4159:6: warning: unused parameter ‘y_start’ [-Wunused-parameter]
src/pngwriter.cc:4159:6: warning: unused parameter ‘angle’ [-Wunused-parameter]
src/pngwriter.cc:4159:6: warning: unused parameter ‘text’ [-Wunused-parameter]
src/pngwriter.cc:4159:6: warning: unused parameter ‘opacity’ [-Wunused-parameter]
src/pngwriter.cc:4159:6: warning: unused parameter ‘red’ [-Wunused-parameter]
src/pngwriter.cc:4159:6: warning: unused parameter ‘green’ [-Wunused-parameter]
src/pngwriter.cc:4159:6: warning: unused parameter ‘blue’ [-Wunused-parameter]
src/pngwriter.cc:4165:6: warning: unused parameter ‘face_path’ [-Wunused-parameter]
 void pngwriter::plot_text_blend( char * face_path, int fontsize, int x_start, int y_start, double angle, char * text, double opacity,  double red, double green, double blue)
      ^
src/pngwriter.cc:4165:6: warning: unused parameter ‘fontsize’ [-Wunused-parameter]
src/pngwriter.cc:4165:6: warning: unused parameter ‘x_start’ [-Wunused-parameter]
src/pngwriter.cc:4165:6: warning: unused parameter ‘y_start’ [-Wunused-parameter]
src/pngwriter.cc:4165:6: warning: unused parameter ‘angle’ [-Wunused-parameter]
src/pngwriter.cc:4165:6: warning: unused parameter ‘text’ [-Wunused-parameter]
src/pngwriter.cc:4165:6: warning: unused parameter ‘opacity’ [-Wunused-parameter]
src/pngwriter.cc:4165:6: warning: unused parameter ‘red’ [-Wunused-parameter]
src/pngwriter.cc:4165:6: warning: unused parameter ‘green’ [-Wunused-parameter]
src/pngwriter.cc:4165:6: warning: unused parameter ‘blue’ [-Wunused-parameter]
src/pngwriter.cc:4172:6: warning: unused parameter ‘face_path’ [-Wunused-parameter]
 void pngwriter::plot_text_utf8_blend( char * face_path, int fontsize, int x_start, int y_start, double angle, char * text, double opacity,  int red, int green, int blue)
      ^
src/pngwriter.cc:4172:6: warning: unused parameter ‘fontsize’ [-Wunused-parameter]
src/pngwriter.cc:4172:6: warning: unused parameter ‘x_start’ [-Wunused-parameter]
src/pngwriter.cc:4172:6: warning: unused parameter ‘y_start’ [-Wunused-parameter]
src/pngwriter.cc:4172:6: warning: unused parameter ‘angle’ [-Wunused-parameter]
src/pngwriter.cc:4172:6: warning: unused parameter ‘text’ [-Wunused-parameter]
src/pngwriter.cc:4172:6: warning: unused parameter ‘opacity’ [-Wunused-parameter]
src/pngwriter.cc:4172:6: warning: unused parameter ‘red’ [-Wunused-parameter]
src/pngwriter.cc:4172:6: warning: unused parameter ‘green’ [-Wunused-parameter]
src/pngwriter.cc:4172:6: warning: unused parameter ‘blue’ [-Wunused-parameter]
src/pngwriter.cc:4178:6: warning: unused parameter ‘face_path’ [-Wunused-parameter]
 void pngwriter::plot_text_utf8_blend( char * face_path, int fontsize, int x_start, int y_start, double angle, char * text, double opacity, double red, double green, double blue)
      ^
src/pngwriter.cc:4178:6: warning: unused parameter ‘fontsize’ [-Wunused-parameter]
src/pngwriter.cc:4178:6: warning: unused parameter ‘x_start’ [-Wunused-parameter]
src/pngwriter.cc:4178:6: warning: unused parameter ‘y_start’ [-Wunused-parameter]
src/pngwriter.cc:4178:6: warning: unused parameter ‘angle’ [-Wunused-parameter]
src/pngwriter.cc:4178:6: warning: unused parameter ‘text’ [-Wunused-parameter]
src/pngwriter.cc:4178:6: warning: unused parameter ‘opacity’ [-Wunused-parameter]
src/pngwriter.cc:4178:6: warning: unused parameter ‘red’ [-Wunused-parameter]
src/pngwriter.cc:4178:6: warning: unused parameter ‘green’ [-Wunused-parameter]
src/pngwriter.cc:4178:6: warning: unused parameter ‘blue’ [-Wunused-parameter]
src/pngwriter.cc:4159:6: warning: unused parameter ‘face_path’ [-Wunused-parameter]
 void pngwriter::plot_text_blend( char * face_path, int fontsize, int x_start, int y_start, double angle, char * text, double opacity, int red, int green, int blue)
      ^
src/pngwriter.cc:4159:6: warning: unused parameter ‘fontsize’ [-Wunused-parameter]
src/pngwriter.cc:4159:6: warning: unused parameter ‘x_start’ [-Wunused-parameter]
src/pngwriter.cc:4159:6: warning: unused parameter ‘y_start’ [-Wunused-parameter]
src/pngwriter.cc:4159:6: warning: unused parameter ‘angle’ [-Wunused-parameter]
src/pngwriter.cc:4159:6: warning: unused parameter ‘text’ [-Wunused-parameter]
src/pngwriter.cc:4159:6: warning: unused parameter ‘opacity’ [-Wunused-parameter]
src/pngwriter.cc:4159:6: warning: unused parameter ‘red’ [-Wunused-parameter]
src/pngwriter.cc:4159:6: warning: unused parameter ‘green’ [-Wunused-parameter]
src/pngwriter.cc:4159:6: warning: unused parameter ‘blue’ [-Wunused-parameter]
src/pngwriter.cc:4165:6: warning: unused parameter ‘face_path’ [-Wunused-parameter]
 void pngwriter::plot_text_blend( char * face_path, int fontsize, int x_start, int y_start, double angle, char * text, double opacity,  double red, double green, double blue)
      ^
src/pngwriter.cc:4165:6: warning: unused parameter ‘fontsize’ [-Wunused-parameter]
src/pngwriter.cc:4165:6: warning: unused parameter ‘x_start’ [-Wunused-parameter]
src/pngwriter.cc:4165:6: warning: unused parameter ‘y_start’ [-Wunused-parameter]
src/pngwriter.cc:4165:6: warning: unused parameter ‘angle’ [-Wunused-parameter]
src/pngwriter.cc:4165:6: warning: unused parameter ‘text’ [-Wunused-parameter]
src/pngwriter.cc:4165:6: warning: unused parameter ‘opacity’ [-Wunused-parameter]
src/pngwriter.cc:4165:6: warning: unused parameter ‘red’ [-Wunused-parameter]
src/pngwriter.cc:4165:6: warning: unused parameter ‘green’ [-Wunused-parameter]
src/pngwriter.cc:4165:6: warning: unused parameter ‘blue’ [-Wunused-parameter]
src/pngwriter.cc:4172:6: warning: unused parameter ‘face_path’ [-Wunused-parameter]
 void pngwriter::plot_text_utf8_blend( char * face_path, int fontsize, int x_start, int y_start, double angle, char * text, double opacity,  int red, int green, int blue)
      ^
src/pngwriter.cc:4172:6: warning: unused parameter ‘fontsize’ [-Wunused-parameter]
src/pngwriter.cc:4172:6: warning: unused parameter ‘x_start’ [-Wunused-parameter]
src/pngwriter.cc:4172:6: warning: unused parameter ‘y_start’ [-Wunused-parameter]
src/pngwriter.cc:4172:6: warning: unused parameter ‘angle’ [-Wunused-parameter]
src/pngwriter.cc:4172:6: warning: unused parameter ‘text’ [-Wunused-parameter]
src/pngwriter.cc:4172:6: warning: unused parameter ‘opacity’ [-Wunused-parameter]
src/pngwriter.cc:4172:6: warning: unused parameter ‘red’ [-Wunused-parameter]
src/pngwriter.cc:4172:6: warning: unused parameter ‘green’ [-Wunused-parameter]
src/pngwriter.cc:4172:6: warning: unused parameter ‘blue’ [-Wunused-parameter]
src/pngwriter.cc:4178:6: warning: unused parameter ‘face_path’ [-Wunused-parameter]
 void pngwriter::plot_text_utf8_blend( char * face_path, int fontsize, int x_start, int y_start, double angle, char * text, double opacity, double red, double green, double blue)
      ^
src/pngwriter.cc:4178:6: warning: unused parameter ‘fontsize’ [-Wunused-parameter]
src/pngwriter.cc:4178:6: warning: unused parameter ‘x_start’ [-Wunused-parameter]
src/pngwriter.cc:4178:6: warning: unused parameter ‘y_start’ [-Wunused-parameter]
src/pngwriter.cc:4178:6: warning: unused parameter ‘angle’ [-Wunused-parameter]
src/pngwriter.cc:4178:6: warning: unused parameter ‘text’ [-Wunused-parameter]
src/pngwriter.cc:4178:6: warning: unused parameter ‘opacity’ [-Wunused-parameter]
src/pngwriter.cc:4178:6: warning: unused parameter ‘red’ [-Wunused-parameter]
src/pngwriter.cc:4178:6: warning: unused parameter ‘green’ [-Wunused-parameter]
src/pngwriter.cc:4178:6: warning: unused parameter ‘blue’ [-Wunused-parameter]

Check New GCC Versions

Looks like the include of <cstring> is missing in gcc 4.8.x for pngwriter.cc

Might should add a test case in travis (but this extends the build matrix -.-)

Installed lib still needs NO_FREETYPE flag

The installed version of pngwriter still requires programs to detect and set the NO_FREETYPE flag if freetype fonts are not found (e.g. here).

That's rather shitty and would be nice if the first install could either remember this (introduce a version.hpp?) or a CMakeModule could set this during find_package.

Remove need of `png.h` in INCLUDE_PATH

Since pngwriter.h is the general include that users include, the third party includes of png.h, zlib.h and ft2build.h are required to reside in their INCLUDE_PATH.

That's not necessary (since we don't use them in interfaces) and a pain with non-default paths.

Related to:

• ComputationalRadiationPhysics/cmake-modules#4
• #7

Found by @psychocoderHPC with a non-default libpng.

Performance with very big Images

The write performance with very big images (above 4K) is pretty poor, see #46.

• Does the internal memory alone harm the performance (#36), can it be optimized?
• Do we call libpng inefficiently for writes?
  • What about using png_write_flush/png_set_flush/png_write_row?
  • Is png_set_interlace_handling really disabled by default and what is the performance impact? Can one play with the ADAM7 passes?
  • play wit png_set_filter?
  • use a better default for setcompressionlevel/PNGWRITER_DEFAULT_COMPRESSION (6) ? (currently, pretty high compression) -> also, there are more zlib parameters with png_set_compression_* to tune! window_bits, buffer_size and mem_level seem worth a look.
• What is PyPNG doing?
• Is libpng itself the bottleneck?

Coverity Scan

This will cause a lot of work :D

Coverity Scan with travis in a special branch.

Check Default Gamma Value

Looks like the default should be 0.5 but sometimes is 0.45 or similar.

Average read functions don't return full color scale

both read(x, y) and dread(x, y) fail to return the full color scale [0-65535] and [0.0-1.0], respectively. The reason most likely is that the multiplication of the internal 8but value with 256 will never reach the last 256 color values.

Can be reproduced with black/white image and the following test case:

#include <pngwriter.h>
#include <iostream>

int main(int argc, char **argv)
{
    if (argc < 2)
        return 1;

    const std::string filename = argv[1];

    const size_t size_x = 256, size_y = 256;

    pngwriter image(size_x, size_y, 0, (filename + std::string(".tmp")).c_str());
    image.readfromfile(filename.c_str());

    size_t width = image.getwidth();
    size_t height = image.getheight();
    size_t bit_depth = image.getbitdepth();

    bool black = false, white = false;
    bool black_int = false, white_int = false;

    std::cout << "bit depth = " << bit_depth << std::endl;

    for (size_t x = 0; x < width; ++x)
        for (size_t y = 0; y < height; ++y)
        {
            /* pngwriter coordinates start at (1,1) and the y direction is inverted */
            int pos_x = 1 + x;
            int pos_y = height - y - 1;

            double color = image.dread(pos_x, pos_y);
            if (color == 0.0)
                black = true;

            if (color == 1.0)
                white = true;

            int col = image.read(pos_x, pos_y);
            if (col == 0)
                black_int = true;

            if (col == 65535 && bit_depth == 16)
                white_int = true;
            if (col == 255 && bit_depth == 8)
                white_int = true;
        }

    image.close();

    if (!(black && white))
        std::cout << "failed double" << std::endl;

    if (!(black_int && white_int))
        std::cout << "failed int" << std::endl;

    return 0;
}

Move Owner Ship to pngwriter Org

• move to organization: https://github.com/pngwriter
• update all links to use new github link #41
• add a nice catchy image to the organization

Doubles in Triangle

In-cooperate patch from
http://sourceforge.net/p/pngwriter/discussion/238247/thread/6e7f2697/

readfromfile: return value & memory leaks on fail

pngwriter::readfromfile as used in examples/pngtest.cc needs a return value.

Else, segfaults will appear as in this example, where the read call failed to to an invalid transform that was applied to the "png object".

Also, memory might be leaked (or it's not sure if memory is leaked since the test segfaults).

Version in pngwriter.h

Is writing 0.55 for 0.5.5 a good idea or should we define major, minor and revision in individual defines?

can we deprecate and in 0.6.0 remove the old define PNGWRITER_VERSION?

Fix Type Casts

Follow up to #10 and the patch from Daniel Hornung provided in Sourceforge Bugs 1:

diff -r e3904f443cd1 pngwriter.cpp
--- a/pngwriter.cpp
+++ b/pngwriter.cpp
@@ -1214,7 +1214,7 @@ void pngwriter::readfromfile(char * name
    png_structp     png_ptr;
    png_infop       info_ptr;
    unsigned char   **image;
-   unsigned long   width, height;
+   png_uint_32   width, height;
    int bit_depth, color_type, interlace_type;
    //   png_uint_32     i;
    //
...

Debian Bugreport #633405

Does this Bug still exist?

http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=633405

Edit: Tested and yes still does...

Check against newer libpng branches

Check against the newer branches of libpng

Compile-test only updates:

• 1.4 #10 #12 55e021d
• 1.5 b0ef022
• 1.6 b0ef022 #56

Newly deprecated functions used by PNGwriter:

• #54 png_convert_to_rfc1123 -> png_convert_to_rfc1123_buffer since version 1.6.0beta03 (and removed in 1.7.0beta59):

Added png_convert_to_rfc1123_buffer() and deprecated png_convert_to_rfc1123()
to avoid including a spurious buffer in the png_struct.

Remove Deprecated png_set_gray call

is that issue fixed by now? -> No

Parameters of `read_png_image`

The private member function read_png_image use pointers (instead of plain png_uint_32) for width and height arguments.

This confuses the Coverity Scan (CID 114042f.) since this would require an input check for NULL before de-referencing and assigning values.

I would therefore propose to change this private signature to use png_uint_32& references instead of pointers (it's pretty c-style currently).

Also, png_get_image_width|height do return real values/copies and a real 0 value in case something went wrong.

Run cppcheck and splint

Run and fix issues uncovered with cppcheck and splint.

Also interesting: -fsanitize=undefined

cppcheck [--enable=all] <pathToDir>

Grayscale Support

Example images: http://www.fnordware.com/superpng/samples.html, and PngSuite
(careful: the pnggrad image does only contain the highest channel value for blue)

• many (all?) functions "force" upgrade up to 16bit like scale...

---

16-bit grayscale images (maybe all greyscale images?)

• readfromfile converts to 8bit without scaling down right (cut off?) for
• reading a 16bit png image does not give the full channel range [0:65535] back in read

---

png file type	readfromfile+read
8-bit/color RGB	ok
8-bit grayscale	broken?
16-bit/color RGB	ok
16-bit grayscale	broken

And palette based images? Forum

---

• the (d)readHSV calls might also be broken and need a check + CI support

---

Note: talking about 8-bit means per channel here. same for 16-bit. Wiki

Creation Time Wrong?

The creation time looks odd (png meta).

# ImageMagick
identify -verbose image.png
# [...]
  Properties:
    Author: Is OK!
    Creation Time: 10 Dec
    date:create: 2015-12-10T18:16:57+01:00
    date:modify: 2015-12-10T18:16:57+01:00
    Description: Is OK, too!
# [...]

Location 1, location 2

Maybe we need to crop the user input/author to strlen 28 ? but description can be longer... hm.
what is the actual length of png_text::text?

filledtriangle / filledtriangle_blend

Reported by Dongkook Park in November 2009.
filledtriangle and filledtriangle_blend

-   y1^=x2;
+   y1^=y2;

@individual61 can you confirm that?

Call for Feedback :)

Add a "call for feedback" section in the readme to motive users to send in the pictures they create with pngwriter.

gcc 4.9.1 warning

I get the following warning when I compile with gcc 4.9.1 and use libpng version 1.6.17

/home/slpp021/workspace/pngwriter/src/pngwriter.cc: In member function ‘void pngwriter::close()’:
/home/slpp021/workspace/pngwriter/src/pngwriter.cc:1081:11: warning: ‘const char* png_convert_to_rfc1123(png_structrp, png_const_timep)’ is deprecated (declared at /home/slpp021/lib/libpng-1.6.17/include/png.h:1175) [-Wdeprecated-declarations]
           png_convert_to_rfc1123(png_ptr, &mod_time),
           ^
/home/slpp021/workspace/pngwriter/src/pngwriter.cc:1081:52: warning: ‘const char* png_convert_to_rfc1123(png_structrp, png_const_timep)’ is deprecated (declared at /home/slpp021/lib/libpng-1.6.17/include/png.h:1175) [-Wdeprecated-declarations]
           png_convert_to_rfc1123(png_ptr, &mod_time),

Add test Routines with .travis.yml

Run the examples and validate the output (hash sums?)

Add proper error handling

Currently there is no error handling except prints with std::err and perror. This means, that it is hard to test if readFromFilefailed or not. Currently it is done like this:

pngwriter png( 1, 1, 0, "tmp.png" );
png.readfromfile( "input.png" );
if ( png.getwidth() == 1 and png.getwidth() == 1 )
    exit( EXIT_FAILURE );

But this check has a false positive for images of size 1x1. These are border cases, but the may not always be unimportant. It would be nice if readFromFile could return some error code.

Remove Freshmeat/Freecode

Freshmeat (later: Freecode) closed June 2014.

Not sure if we still need the links or if listing in the new Freshcode.club is necessary (imho: not for now).

Memory Leak in operator= ?

Does the memory leak reported here still exist in the release-0.5.5 branch?
https://sourceforge.net/p/pngwriter/discussion/238247/thread/c7607b9b/

Remove Duplicated Files

Hey @individual61 - do you think it's fine if we remove all the copied and translated Spanish files in 0.6.0 onwards?

It is just a huge pain to update them and the code is super duplicated :(

`graph_` Dereference after NULL Check

There are quite a few usages of graph_ even if a NULL check failed and did print warnings to stderr.

Coverity Scan CID 114014-114024

Value degradation when calling pngwriter::plot with float values

I was implementing a unit test for a read/write function using pngwriter and found the following problem. Some input values, like 0.868921399117f were degrading to smaller and smaller values when chaining calls to read and plot. (More exactly I really wrote out the png and then read it in anew).

After roughly 120 iterations the value reaches a fix value of 0.868925001907f. When representing this as the pngwriter internal integer this means the first value of 56945 degraded down to 56831 thereby loosing quite a bit of precision.

The problem is the simple cast to int in pngwriter::plot(int, int, double, double, double). Here is an example reproducing the problem and showing two possible bugfixes.

    #include <iostream>
    int main(void)
    {
        float originalValue = 0.868921399117;
        for ( int i = 0; i < 120; ++i )
        {
            /* call pngwriter.plot which only exists with double arguments */
            double doubleValueToPlot = double( originalValue );
            /* the double version calls the int version with a cast wich always
             * rounds using floor which results in value degradataion */
            int intToPlot = int( doubleValueToPlot*65535 );
            std::cout << "Plot int: " << intToPlot << "\n";
            /* the int is written out without loss and then normally you would
             * try to reconstruct the original float: */
            float readInValue = (float) intToPlot / 65535;
            originalValue = readInValue;
        }

        std::cout << "=== Bugfix 1 ===\n";
        originalValue = 0.868921399117;
        for ( int i = 0; i < 10; ++i )
        {
            /* add a plot function in pngwriter accepting float */
            float valueToPlot = float( originalValue );
            int intToPlot = int( valueToPlot*65535 );
            std::cout << "Plot int: " << intToPlot << "\n";
            float readInValue = (float) intToPlot / 65535;
            originalValue = readInValue;
        }

        std::cout << "=== Bugfix 2 ===\n";
        originalValue = 0.868921399117;
        for ( int i = 0; i < 10; ++i )
        {
            double doubleValueToPlot = double( originalValue );
            /* round correctly instead of doing a direct floor-like int cast */
            auto round = []( double x ) -> int {
                return (x > 0.0) ? (x + 0.5) : (x - 0.5);
            };
            int intToPlot = round( doubleValueToPlot*65535 );
            std::cout << "Plot int: " << intToPlot << "\n";
            float readInValue = (float) intToPlot / 65535;
            originalValue = readInValue;
        }
    }

Note that Bugfix 1 converges to 56944 but bugfix 2 converges to 56945. The latter is more correct, because the input was: 56944.7638911

Return Values: 0 is Success

many functions use 0 as an integer error return code and 1 or something higher as success

• read_png_image
• read_png_info
• check_if_png
• ...

this is against common sense, where 0 is always the successful result in the coding world.

One could/should also define enums for those magic numbers (at least for success).