/// <summary>
/// Encodes the provided BGRA, Y flipped, pixel data to a PNG image.
/// </summary>
/// <param name="pixels">The pixel date to encode.</param>
/// <param name="width">The width of the image in the data.</param>
/// <param name="height">The height of the image in the data.</param>
/// <returns>A PNG image as bytes.</returns>
public static byte[] Encode(byte[] pixels, int width, int height)
{
var pngHeader = new byte[] { 0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A };
const int maxBlockSize = 0xFFFF;
using var stream = new MemoryStream();
// Write the png header.
stream.Write(pngHeader, 0, 8);
var header = new PngFileHeader
{
Width = width,
Height = height,
ColorType = 6,
BitDepth = 8,
FilterMethod = 0,
CompressionMethod = 0,
InterlaceMethod = 0
};
// Write header chunk.
var chunkData = new byte[13];
WriteInteger(chunkData, 0, header.Width);
WriteInteger(chunkData, 4, header.Height);
chunkData[8] = header.BitDepth;
chunkData[9] = header.ColorType;
chunkData[10] = header.CompressionMethod;
chunkData[11] = header.FilterMethod;
chunkData[12] = header.InterlaceMethod;
WriteChunk(stream, PngChunkTypes.HEADER, chunkData);
// Write data chunks.
var data = new byte[width * height * 4 + height];
int rowLength = width * 4 + 1;
for (var y = 0; y < height; y++)
{
data[y * rowLength] = 0;
for (var x = 0; x < width; x++)
{
// Calculate the offset for the new array.
int dataOffset = y * rowLength + x * 4 + 1;
// Calculate the offset for the original pixel array.
int pixelOffset = (y * width + x) * 4;
data[dataOffset + 0] = pixels[pixelOffset + 2];
data[dataOffset + 1] = pixels[pixelOffset + 1];
data[dataOffset + 2] = pixels[pixelOffset + 0];
data[dataOffset + 3] = pixels[pixelOffset + 3];
}
}
byte[] buffer = ZlibStreamUtility.Compress(data, 6);
int numChunks = buffer.Length / maxBlockSize;
if (buffer.Length % maxBlockSize != 0)
{
numChunks++;
}
for (var i = 0; i < numChunks; i++)
{
int length = buffer.Length - i * maxBlockSize;
if (length > maxBlockSize)
{
length = maxBlockSize;
}
WriteChunk(stream, PngChunkTypes.DATA, buffer, i * maxBlockSize, length);
}
// Write end chunk.
WriteChunk(stream, PngChunkTypes.END, null);
stream.Flush();
return(stream.ToArray());
}
/// <summary>
/// Encodes the provided Y flipped pixel data to a PNG image.
/// </summary>
/// <param name="pixels">The pixel date to encode.</param>
/// <param name="size">The size of the image..</param>
/// <param name="format">The format of the pixel data.</param>
/// <returns>A PNG image as bytes.</returns>
public static byte[] Encode(byte[] pixels, Vector2 size, PixelFormat format)
{
using var stream = new MemoryStream();
stream.Write(_pngHeader, 0, 8);
// Write header chunk.
var chunkData = new byte[13];
var width = (int)size.X;
var height = (int)size.Y;
WriteInteger(chunkData, 0, width);
WriteInteger(chunkData, 4, height);
var header = new PngFileHeader
{
Size = size,
ColorType = (byte)(format == PixelFormat.Red ? 0 : 6), // Greyscale, otherwise RGBA
BitDepth = 8,
FilterMethod = 0,
CompressionMethod = 0,
InterlaceMethod = 0,
PixelFormat = format
};
chunkData[8] = header.BitDepth;
chunkData[9] = header.ColorType;
chunkData[10] = header.CompressionMethod;
chunkData[11] = header.FilterMethod;
chunkData[12] = header.InterlaceMethod;
WriteChunk(stream, PngChunkTypes.HEADER, chunkData);
// Write data chunks.
int bytesPerPixel = Gl.PixelFormatToComponentCount(format);
var data = new byte[width * height * bytesPerPixel + height];
int rowLength = width * bytesPerPixel + 1; // One byte for the filter
for (var y = 0; y < height; y++)
{
data[y * rowLength] = 0;
for (var x = 0; x < width; x++)
{
// Calculate the offset for the new array.
int dataOffset = y * rowLength + x * bytesPerPixel + 1;
// Calculate the offset for the original pixel array.
int pixelOffset = (y * width + x) * bytesPerPixel;
if (format == PixelFormat.Rgba)
{
data[dataOffset + 0] = pixels[pixelOffset + 0];
data[dataOffset + 1] = pixels[pixelOffset + 1];
data[dataOffset + 2] = pixels[pixelOffset + 2];
data[dataOffset + 3] = pixels[pixelOffset + 3];
}
else if (format == PixelFormat.Bgra)
{
data[dataOffset + 0] = pixels[pixelOffset + 2];
data[dataOffset + 1] = pixels[pixelOffset + 1];
data[dataOffset + 2] = pixels[pixelOffset + 0];
data[dataOffset + 3] = pixels[pixelOffset + 3];
}
else if (format == PixelFormat.Red)
{
data[dataOffset] = pixels[pixelOffset];
}
else
{
throw new Exception($"Unsupported encoding pixel format - {format}");
}
}
}
// Compress data.
byte[] buffer = ZlibStreamUtility.Compress(data, 6);
int numChunks = buffer.Length / MAX_BLOCK_SIZE;
if (buffer.Length % MAX_BLOCK_SIZE != 0)
{
numChunks++;
}
for (var i = 0; i < numChunks; i++)
{
int length = buffer.Length - i * MAX_BLOCK_SIZE;
if (length > MAX_BLOCK_SIZE)
{
length = MAX_BLOCK_SIZE;
}
WriteChunk(stream, PngChunkTypes.DATA, buffer, i * MAX_BLOCK_SIZE, length);
}
// Write end chunk.
WriteChunk(stream, PngChunkTypes.END, null);
stream.Flush();
return(stream.ToArray());
}
