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Handle black point issue in CMYK

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BobLd
2023-04-22 23:51:11 +01:00
parent be9a9d7892
commit 254321e906
1 changed files with 44 additions and 24 deletions
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68
src/UglyToad.PdfPig/Graphics/Colors/ColorSpaceDetails.cs
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@@ -1259,22 +1259,32 @@
/// <inheritdoc/>
internal override double[] Process(params double[] values)
{
// TODO - use ICC profile
if (Profile != null && Profile.TryProcess(values, out double[] xyz) && xyz.Length == 3)
if (Profile != null)
{
double x = xyz[0];
double y = xyz[1];
double z = xyz[2];
if (Profile.Header.Pcs == IccProfileConnectionSpace.PCSXYZ)
if (Profile.Header.ColourSpace == IccColourSpaceType.CMYK && values[0] == 0 && values[1] == 0 && values[2] == 0 && values[3] == 1)
{
var rgb = colorSpaceTransformer.TransformXYZToRGB((x, y, z));
return new double[] { rgb.R, rgb.G, rgb.B };
// See 'COLOR MANAGEMENT UNDERSTANDING AND USING ICC PROFILES' by Phil Green:
// Issues in CMYK Workflows
// Pure black (0–0–0–K) turns into four-color C–M–Y–K color build, with resulting color shift,
// misregister, and / or trap implications. Also known as the black type problem.
return new double[] { 0, 0, 0 };
}
else
if (Profile.TryProcess(values, out double[] xyz) && xyz.Length == 3)
{
return labColorSpaceDetails.Process(x * 100.0, y * 255.0 - 128.0, z * 255.0 - 128.0); // need to scale
double x = xyz[0];
double y = xyz[1];
double z = xyz[2];
if (Profile.Header.Pcs == IccProfileConnectionSpace.PCSXYZ)
{
var rgb = colorSpaceTransformer.TransformXYZToRGB((x, y, z));
return new double[] { rgb.R, rgb.G, rgb.B };
}
else
{
return labColorSpaceDetails.Process(x * 100.0, y * 255.0 - 128.0, z * 255.0 - 128.0); // need to scale
}
}
}
@@ -1289,22 +1299,32 @@
throw new ArgumentException($"Invalid number of imputs, expecting {NumberOfColorComponents} but got {values.Length}", nameof(values));
}
// TODO - use ICC profile
if (Profile != null && Profile.TryProcess(values, out double[] xyz) && xyz.Length == 3)
if (Profile != null)
{
double x = xyz[0];
double y = xyz[1];
double z = xyz[2];
if (Profile.Header.Pcs == IccProfileConnectionSpace.PCSXYZ)
if (Profile.Header.ColourSpace == IccColourSpaceType.CMYK && values[0] == 0 && values[1] == 0 && values[2] == 0 && values[3] == 1)
{
var rgb = colorSpaceTransformer.TransformXYZToRGB((x, y, z));
return new RGBColor((decimal)rgb.R, (decimal)rgb.G, (decimal)rgb.B);
// See 'COLOR MANAGEMENT UNDERSTANDING AND USING ICC PROFILES' by Phil Green:
// Issues in CMYK Workflows
// Pure black (0–0–0–K) turns into four-color C–M–Y–K color build, with resulting color shift,
// misregister, and / or trap implications. Also known as the black type problem.
return RGBColor.Black;
}
else
if (Profile.TryProcess(values, out double[] xyz) && xyz.Length == 3)
{
return labColorSpaceDetails.GetColor(x, y, z);
double x = xyz[0];
double y = xyz[1];
double z = xyz[2];
if (Profile.Header.Pcs == IccProfileConnectionSpace.PCSXYZ)
{
var (R, G, B) = colorSpaceTransformer.TransformXYZToRGB((x, y, z));
return new RGBColor((decimal)R, (decimal)G, (decimal)B);
}
else
{
return labColorSpaceDetails.GetColor(x, y, z);
}
}
}