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add device cmyk support for png conversion

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This commit is contained in:
Eliot Jones
2021-02-08 18:27:49 -04:00
parent c19742a2ae
commit 68dd3f5a75
1 changed files with 27 additions and 7 deletions
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34
src/UglyToad.PdfPig/Images/Png/PngFromPdfImageFactory.cs
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@@ -14,7 +14,8 @@
var actualColorSpace = hasValidDetails ? image.ColorSpaceDetails.BaseType : image.ColorSpace; var actualColorSpace = hasValidDetails ? image.ColorSpaceDetails.BaseType : image.ColorSpace;
var isColorSpaceSupported = var isColorSpaceSupported =
actualColorSpace == ColorSpace.DeviceGray || actualColorSpace == ColorSpace.DeviceRGB; actualColorSpace == ColorSpace.DeviceGray || actualColorSpace == ColorSpace.DeviceRGB
|| actualColorSpace == ColorSpace.DeviceCMYK;
if (!isColorSpaceSupported || !image.TryGetBytes(out var bytesPure)) if (!isColorSpaceSupported || !image.TryGetBytes(out var bytesPure))
{ {
@@ -25,7 +26,7 @@
try try
{ {
var is3Byte = actualColorSpace == ColorSpace.DeviceRGB; var is3Byte = actualColorSpace == ColorSpace.DeviceRGB || actualColorSpace == ColorSpace.DeviceCMYK;
var multiplier = is3Byte ? 3 : 1; var multiplier = is3Byte ? 3 : 1;
var builder = PngBuilder.Create(image.WidthInSamples, image.HeightInSamples, false); var builder = PngBuilder.Create(image.WidthInSamples, image.HeightInSamples, false);
@@ -38,18 +39,37 @@
} }
var i = 0; var i = 0;
for (var y = 0; y < image.HeightInSamples; y++) for (var col = 0; col < image.HeightInSamples; col++)
{ {
for (var x = 0; x < image.WidthInSamples; x++) for (var row = 0; row < image.WidthInSamples; row++)
{ {
if (is3Byte) if (actualColorSpace == ColorSpace.DeviceCMYK)
{ {
builder.SetPixel(bytesPure[i++], bytesPure[i++], bytesPure[i++], x, y); /*
* Where CMYK in 0..1
* R = 255 × (1-C) × (1-K)
* G = 255 × (1-M) × (1-K)
* B = 255 × (1-Y) × (1-K)
*/
var c = (bytesPure[i++]/255d);
var m = (bytesPure[i++]/255d);
var y = (bytesPure[i++]/255d);
var k = (bytesPure[i++]/255d);
var r = (byte)(255 * (1 - c) * (1 - k));
var g = (byte)(255 * (1 - m) * (1 - k));
var b = (byte)(255 * (1 - y) * (1 - k));
builder.SetPixel(r, g, b, row, col);
}
else if (is3Byte)
{
builder.SetPixel(bytesPure[i++], bytesPure[i++], bytesPure[i++], row, col);
} }
else else
{ {
var pixel = bytesPure[i++]; var pixel = bytesPure[i++];
builder.SetPixel(pixel, pixel, pixel, x, y); builder.SetPixel(pixel, pixel, pixel, row, col);
} }
} }
} }