private static bool tryGetTagEntry(TagEntry[] entries, uint tag, out TagEntry entry)
{
for (int i = 0; i < entries.Length; i++)
{
if (entries[i].tag == tag)
{
entry = entries[i];
return(true);
}
}
entry = default;
return(false);
}
public static ColorProfile Parse(ReadOnlySpan <byte> prof)
{
const int headerLength = 128;
const int headerPlusTagCountLength = 132;
if (prof.Length < headerPlusTagCountLength)
{
return(invalidProfile);
}
uint len = ReadUInt32BigEndian(prof.Slice(0, sizeof(uint)));
if (len != prof.Length)
{
return(invalidProfile);
}
uint acsp = ReadUInt32BigEndian(prof.Slice(36));
var ver = prof.Slice(8, 4);
if ((ver[0] != 2 && ver[0] != 4) || acsp != IccStrings.acsp)
{
return(invalidProfile);
}
var dataColorSpace = ReadUInt32BigEndian(prof.Slice(16)) switch {
IccStrings.RGB => ProfileColorSpace.Rgb,
IccStrings.GRAY => ProfileColorSpace.Grey,
IccStrings.CMYK => ProfileColorSpace.Cmyk,
_ => ProfileColorSpace.Other
};
var pcsColorSpace = ReadUInt32BigEndian(prof.Slice(20)) switch {
IccStrings.XYZ => ProfileColorSpace.Xyz,
IccStrings.Lab => ProfileColorSpace.Lab,
_ => ProfileColorSpace.Other
};
if (pcsColorSpace != ProfileColorSpace.Xyz || (dataColorSpace != ProfileColorSpace.Rgb && dataColorSpace != ProfileColorSpace.Grey))
{
return(new ColorProfile(prof.ToArray(), dataColorSpace, pcsColorSpace, ColorProfileType.Unknown));
}
uint tagCount = ReadUInt32BigEndian(prof.Slice(headerLength));
if (len < (headerPlusTagCountLength + tagCount * Unsafe.SizeOf <TagEntry>()))
{
return(invalidProfile);
}
var tagEntries = new TagEntry[((int)tagCount)];
for (int i = 0; i < tagCount; i++)
{
int entryStart = headerPlusTagCountLength + i * Unsafe.SizeOf <TagEntry>();
uint tag = ReadUInt32BigEndian(prof.Slice(entryStart));
uint pos = ReadUInt32BigEndian(prof.Slice(entryStart + 4));
uint cb = ReadUInt32BigEndian(prof.Slice(entryStart + 8));
if (len < (pos + cb))
{
return(invalidProfile);
}
// not handling these yet, so we'll hand off to WCS
if (tag == IccTags.A2B0 || tag == IccTags.B2A0)
{
return(new ColorProfile(prof.ToArray(), dataColorSpace, pcsColorSpace, ColorProfileType.Table));
}
tagEntries[i] = new TagEntry(tag, (int)pos, (int)cb);
}
if (dataColorSpace == ProfileColorSpace.Grey &&
tryGetTagEntry(tagEntries, IccTags.kTRC, out var kTRC) &&
tryGetCurve(prof.Slice(kTRC.pos, kTRC.cb), out var curve)
)
{
if (curve == sRGB.Curve)
{
return(sGrey);
}
return(new CurveProfile(prof.ToArray(), curve, dataColorSpace, pcsColorSpace));
}
if (dataColorSpace == ProfileColorSpace.Rgb &&
tryGetTagEntry(tagEntries, IccTags.bTRC, out var bTRC) &&
tryGetTagEntry(tagEntries, IccTags.gTRC, out var gTRC) &&
tryGetTagEntry(tagEntries, IccTags.rTRC, out var rTRC) &&
tryGetTagEntry(tagEntries, IccTags.bXYZ, out var bXYZ) &&
tryGetTagEntry(tagEntries, IccTags.gXYZ, out var gXYZ) &&
tryGetTagEntry(tagEntries, IccTags.rXYZ, out var rXYZ)
)
{
var bTRCData = prof.Slice(bTRC.pos, bTRC.cb);
var gTRCData = prof.Slice(gTRC.pos, gTRC.cb);
var rTRCData = prof.Slice(rTRC.pos, rTRC.cb);
if (bTRCData.SequenceEqual(gTRCData) && bTRCData.SequenceEqual(rTRCData) &&
tryGetCurve(bTRCData, out var rgbcurve) &&
tryGetMatrix(prof.Slice(bXYZ.pos, bXYZ.cb), prof.Slice(gXYZ.pos, gXYZ.cb), prof.Slice(rXYZ.pos, rXYZ.cb), out var matrix)
)
{
if (matrix.IsRouglyEqualTo(sRGB.Matrix) && rgbcurve == sRGB.Curve)
{
return(sRGB);
}
var imatrix = matrix.InvertPrecise();
if (!imatrix.IsNaN())
{
return(new MatrixProfile(prof.ToArray(), matrix, imatrix, rgbcurve, dataColorSpace, pcsColorSpace));
}
}
}
return(invalidProfile);
}