public static void SaveImageData(Stream stream, FreeImageBitmap image)
{
byte[] imageData = new byte[image.Width * image.Height / 2];
int o = 0;
for (int y = 0; y < image.Height; y++)
{
if (image.ColorDepth == 4)
{
var scanline = image.GetScanlineFromTop4Bit(y);
for (int x = 0; x < image.Width; x += 2)
{
int p1 = scanline[x];
int p2 = scanline[x + 1];
imageData[o++] = (byte)((p1 << 4) + p2);
}
}
else if (image.ColorDepth == 8)
{
var scanline = image.GetScanlineFromTop8Bit(y);
for (int x = 0; x < image.Width; x += 2)
{
int p1 = scanline[x] & 0x0F;
int p2 = scanline[x + 1] & 0x0F;
imageData[o++] = (byte)((p1 << 4) + p2);
}
}
}
byte[] bytes = new byte[imageData.Length];
int[] lengths = new int[9];
TransformImage(bytes, imageData, image.Width, image.Height);
int height = image.Height;
//encode the bytes
for (int i = 0; i < bytes.Length; i++)
{
int x = i / image.Height;
int p = x & 3;
Array.Clear(lengths, 0, lengths.Length);
lengths[0] = MeasureRleRun(bytes, i, height);
lengths[1] = MeasureRleRun2(bytes, i, height);
lengths[2] = MeasurePreviousColumnRun(bytes, i, height, height * 4, 0);
if (p >= 1)
{
lengths[3] = MeasurePreviousColumnRun(bytes, i, height, height * p, 0);
lengths[6] = MeasurePreviousColumnRun(bytes, i, height, height * p, 255);
}
if (p >= 2)
{
lengths[4] = MeasurePreviousColumnRun(bytes, i, height, height * (p - 1), 0);
lengths[7] = MeasurePreviousColumnRun(bytes, i, height, height * (p - 1), 255);
}
if (p >= 3)
{
lengths[5] = MeasurePreviousColumnRun(bytes, i, height, height * (p - 2), 0);
lengths[8] = MeasurePreviousColumnRun(bytes, i, height, height * (p - 2), 255);
}
int maxIndex;
int max = lengths.Max(out maxIndex);
byte b = bytes[i];
if (max < 2)
{
maxIndex = -1;
}
else if (max == 2)
{
if (b >= 0x08)
{
maxIndex = -1;
}
else
{
if (maxIndex < 2 || maxIndex >= 6)
{
maxIndex = -1;
}
}
}
else if (max == 3)
{
//don't compress 3 bytes to 3 bytes unless first byte would be a literal
if (b >= 0x08 && maxIndex < 2 || maxIndex >= 6)
{
maxIndex = -1;
}
}
switch (maxIndex)
{
default:
{
//No compression - raw byte or escaped literal
if (b >= 0x08)
{
//raw byte
stream.WriteByte((byte)b);
}
else
{
//encode a literal as 2 bytes
stream.WriteByte((byte)0x07);
stream.WriteByte((byte)b);
}
i++;
}
break;
case 0:
{
//RLE - 01
stream.WriteByte(0x01);
stream.WriteByte((byte)(max - 1));
stream.WriteByte(b);
i += max;
}
break;
case 1:
{
//Alternating RLE - 02
stream.WriteByte(0x02);
stream.WriteByte((byte)(max / 2 - 1));
stream.WriteByte(b);
stream.WriteByte(bytes[i + 1]);
i += max;
}
break;
case 2:
{
//from previous column (same plane) - 00
stream.WriteByte(0x00);
stream.WriteByte((byte)(max - 1));
i += max;
}
break;
case 3:
{
//from plane 0 without mask - 03
stream.WriteByte(0x03);
stream.WriteByte((byte)(max - 1));
i += max;
}
break;
case 6:
{
//from plane 0 with mask - 06 03
stream.WriteByte(0x06);
stream.WriteByte(0x03);
stream.WriteByte((byte)(max - 1));
i += max;
}
break;
case 4:
{
//from plane 1 without mask - 04
stream.WriteByte(0x04);
stream.WriteByte((byte)(max - 1));
i += max;
}
break;
case 7:
{
//from plane 1 with mask - 06 04
stream.WriteByte(0x06);
stream.WriteByte(0x04);
stream.WriteByte((byte)(max - 1));
i += max;
}
break;
case 5:
{
//from plane 2 without mask - 05
stream.WriteByte(0x05);
stream.WriteByte((byte)(max - 1));
i += max;
}
break;
case 8:
{
//from plane 2 with mask - 06 05
stream.WriteByte(0x06);
stream.WriteByte(0x05);
stream.WriteByte((byte)(max - 1));
i += max;
}
break;
}
i--;
}
}
