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Improve UnpackComponents() method performance

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This commit is contained in:
BobLd
2024-02-06 11:00:49 +00:00
parent a6eb6c952c
commit f78b15a614
1 changed files with 10 additions and 6 deletions
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16
src/UglyToad.PdfPig/Images/ColorSpaceDetailsByteConverter.cs
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@@ -51,18 +51,22 @@
private static byte[] UnpackComponents(IReadOnlyList<byte> input, int bitsPerComponent)
{
IEnumerable<byte> Unpack(byte b)
{
int right = (int)Math.Pow(2, bitsPerComponent) - 1;
int end = 8 - bitsPerComponent;
var unpacked = new byte[input.Count * (int)Math.Ceiling((end + 1) / (double)bitsPerComponent)];
int right = (int)Math.Pow(2, bitsPerComponent) - 1;
int u = 0;
foreach (byte b in input)
{
// Enumerate bits in bitsPerComponent-sized chunks from MSB to LSB, masking on the appropriate bits
for (int i = 8 - bitsPerComponent; i >= 0; i -= bitsPerComponent)
for (int i = end; i >= 0; i -= bitsPerComponent)
{
yield return (byte)((b >> i) & right);
unpacked[u++] = (byte)((b >> i) & right);
}
}
return input.SelectMany(Unpack).ToArray();
return unpacked;
}
private static byte[] RemoveStridePadding(byte[] input, int strideWidth, int imageWidth, int imageHeight, int multiplier)