tjhann/imagefmt

Image loading/saving. @nogc

imagefmt

Image loader and saver for simple needs with support for custom IO and allocators. Independent of the garbage collector.

Decoders:

• PNG, 8-bit and 16-bit interlaced and paletted (+tRNS chunk)
• BMP, 8-bit
• TGA, 8-bit non-paletted
• JPEG, baseline

Encoders:

• PNG, 8-bit non-paletted non-interlaced
• BMP, 8-bit RGB RGBA
• TGA, 8-bit

Returned buffers are 8-bit by default, other options are 16-bit and 8/16-bit based on source data. The top-left corner is at (0, 0) by default.

import imagefmt;

IFImage a = read_image("aya.jpg", 3);     // convert to rgb
if (a.e) {
    printf("*** load error: %s\n", IF_ERROR[a.e].ptr);
    return;
}
scope(exit) a.free();

IFInfo info = read_info("vine.tga");
printf("size: %d x %d   components: %d\n", info.w, info.h, info.c);

imagefmt's Issues

Inifinite loop on empty buffer

code:

ubyte[] buf;
IFImage a = read_image(buf);

I fixed it changing the initial if in init_reader to:

ubyte init_reader(Reader* rc, Read io, ubyte[] buf)
{
    if (buf.length < 16) {
        return buf.length ? ERROR.lackdata : ERROR.nodata;
    }
...

Support flipping images vertically.

One quirk of OpenGL and some other graphics APIs is that the (0, 0) is expected to be at the bottom left corner of the image, whereas most image formats place (0, 0) at the top left. This usually relates to how Y-axis coordinates are projected (with OpenGL placing Y:0 at the bottom of the screen).

A number of image libraries provide flags or functions to perform this flipping behaviour,
ie. stb_image provides:

stbi_set_flip_vertically_on_load(true);

Which indicates that subsequent images should be loaded with their Y-axes reversed.

Implementing this at application level can be tricky, since some image formats (BMP) are stored bottom-up, whereas others are stored top-down.