Transparency issues when generating jpeg image

[gowengit]

Transparency issues when generating jpeg image

[mKenfenheuer]

Thanks for your help, this pointed me into the right direction.

Your code worked well, but not a 100% fit for my case (i had also transparent font smoothing).

I Just had to create a white image and "print" the document onto it.

the code below now works for me:

public static byte[] ConvertPdfToJpeg(this byte[] data, int rwidth = 1080, int rheight = 1920)
        {
            using (var library = DocLib.Instance)
            {
                using (var docReader = library.GetDocReader(data, rwidth, rheight))
                {
                    using (var pageReader = docReader.GetPageReader(0))
                    {
                        var rawBytes = pageReader.GetImage();
                        var width = pageReader.GetPageWidth();
                        var height = pageReader.GetPageHeight();
                        using (var doc = new Bitmap(width, height, PixelFormat.Format32bppArgb))
                        using (var bmp = new Bitmap(width, height, PixelFormat.Format32bppArgb))
                        {
                            bmp.AddBytes(rawBytes);
                            for (int y = 0; y < bmp.Height; y++)
                            {
                                bmp.SetPixel(bmp.Width - 1, y, bmp.GetPixel(bmp.Width - 2, y));
                            }
                            Graphics g = Graphics.FromImage(doc);
                            g.FillRegion(Brushes.White, new Region(new Rectangle(0, 0, width, height)));
                            g.DrawImage(bmp, new Point(0, 0));
                            g.Save();
                            using (var stream = new MemoryStream())
                            {
                                doc.Save(stream, ImageFormat.Jpeg);
                                return stream.ToArray();
                            }
                        }
                    }
                }
            }
        }

[jaredbaszler]

@mKenfenheuer

Thanks for your help, this pointed me into the right direction.

Your code worked well, but not a 100% fit for my case (i had also transparent font smoothing).

I Just had to create a white image and "print" the document onto it.

the code below now works for me:

public static byte[] ConvertPdfToJpeg(this byte[] data, int rwidth = 1080, int rheight = 1920)
        {
            using (var library = DocLib.Instance)
            {
                using (var docReader = library.GetDocReader(data, rwidth, rheight))
                {
                    using (var pageReader = docReader.GetPageReader(0))
                    {
                        var rawBytes = pageReader.GetImage();
                        var width = pageReader.GetPageWidth();
                        var height = pageReader.GetPageHeight();
                        using (var doc = new Bitmap(width, height, PixelFormat.Format32bppArgb))
                        using (var bmp = new Bitmap(width, height, PixelFormat.Format32bppArgb))
                        {
                            bmp.AddBytes(rawBytes);
                            for (int y = 0; y < bmp.Height; y++)
                            {
                                bmp.SetPixel(bmp.Width - 1, y, bmp.GetPixel(bmp.Width - 2, y));
                            }
                            Graphics g = Graphics.FromImage(doc);
                            g.FillRegion(Brushes.White, new Region(new Rectangle(0, 0, width, height)));
                            g.DrawImage(bmp, new Point(0, 0));
                            g.Save();
                            using (var stream = new MemoryStream())
                            {
                                doc.Save(stream, ImageFormat.Jpeg);
                                return stream.ToArray();
                            }
                        }
                    }
                }
            }
        }

@mKenfenheuer - thanks a bunch. I had exactly the same problem as you had experienced. You saved me a BUNCH of time. Thanks for the code example!!!

[inlineHamed]

I think the library should treat like this as default.

[Modest-as]

This is not an issue, the library will generate whatever is presented in the PDF file, if file has no background specified it will treat that as transparent, you can always specify background layer to whichever color you want depending on your image processing library, just replace empty pixels with whatever Format32bppArgb value you want

[mKenfenheuer]

@Modest-as

do you have an example on how to do this?

[Modest-as]

Sure, something like this:

var rawBytes = pageReader.GetImage();

for (var i = 0; i < rawBytes.Length / 4; i++)
{
    var j = i * 4;
    var alpha = rawBytes[j];
    var red = rawBytes[j + 1];
    var green = rawBytes[j + 2];
    var blue = rawBytes[j + 3];

    if (alpha != 0 || red != 0 || green != 0 || blue != 0) continue;

    rawBytes[j] = byte.MaxValue;
    rawBytes[j + 1] = byte.MaxValue;
    rawBytes[j + 2] = byte.MaxValue;
    rawBytes[j + 3] = byte.MaxValue;
}