回答編集履歴
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コメントを受け変換部追記。
test
CHANGED
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@@ -37,3 +37,129 @@
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あと、質問を編集しただけでは私には通知が来ないようなので回答にコメントしてもらえると反応が早いかもしれません。
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【コメントを受け追記】
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減色済みの奴が対象で減勘だけするならこんな感じで良いはず。
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例外処理とか諸々省略してるので注意。
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```C#
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static Bitmap ImageConvert24bitTo8bit(Bitmap bmpSource)
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{
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Bitmap bmp8bit = new Bitmap(bmpSource.Width, bmpSource.Height, PixelFormat.Format8bppIndexed);
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BitmapData bmpData8bit = bmp8bit.LockBits(
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new Rectangle(0, 0, bmp8bit.Width, bmp8bit.Height),
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ImageLockMode.WriteOnly,
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bmp8bit.PixelFormat
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);
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BitmapData bmpData24bit = bmpSource.LockBits(
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new Rectangle(0, 0, bmpSource.Width, bmpSource.Height),
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ImageLockMode.ReadOnly,
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bmpSource.PixelFormat
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);
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byte[] imgBuf8bit = new byte[bmpData8bit.Stride * bmp8bit.Height];
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byte[] imgBuf24bit = new byte[bmpData24bit.Stride * bmpSource.Height];
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Marshal.Copy(bmpData24bit.Scan0, imgBuf24bit, 0, imgBuf24bit.Length);
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var colors = new Dictionary<Color, byte>();
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byte colorIndex = 0;
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for (int y = 0; y < bmpSource.Height; y++)
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{
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for (int x = 0; x < bmpSource.Width; x++)
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{
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int index24bit = y * bmpData24bit.Stride + x * 3;
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int index8bit = y * bmpData8bit.Stride + x;
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byte b = imgBuf24bit[index24bit];
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byte g = imgBuf24bit[index24bit + 1];
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byte r = imgBuf24bit[index24bit + 2];
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// 24bitから8bitへ
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var color = Color.FromArgb(r, g, b);
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if (colors.TryGetValue(color, out byte i))
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imgBuf8bit[index8bit] = i;
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else
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{
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imgBuf8bit[index8bit] = colorIndex;
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colors.Add(color, colorIndex);
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colorIndex++;
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}
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}
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}
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Marshal.Copy(imgBuf8bit, 0, bmpData8bit.Scan0, imgBuf8bit.Length);
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bmpSource.UnlockBits(bmpData24bit);
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bmp8bit.UnlockBits(bmpData8bit);
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var pal = bmp8bit.Palette;
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foreach (var item in colors)
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pal.Entries[item.Value] = item.Key;
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bmp8bit.Palette = pal;
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return bmp8bit;
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}
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```
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