/// <summary>
/// Perform the readback from the provided Render texture using ReadPixels API.
/// </summary>
/// <param name="renderTexture">Input source Render texture for the readback.</param>
/// <returns>Returns a byte array of the RGB data retrieved from the readback.</returns>
/// <exception cref="NotSupportedException"></exception>
public static byte[] GetPixelsSlow(RenderTexture renderTexture)
{
using (s_GetPixelsSlow.Auto())
{
var pixelSize = GraphicsUtilities.GetBlockSize(renderTexture.graphicsFormat);
var channels = GraphicsFormatUtility.GetComponentCount(renderTexture.graphicsFormat);
var channelSize = pixelSize / channels;
var rect = new Rect(0, 0, renderTexture.width, renderTexture.height);
// for RGB(A) we can just return the raw data.
if (channels >= 3 && channels <= 4)
{
var texture = new Texture2D(renderTexture.width, renderTexture.height, renderTexture.graphicsFormat, TextureCreationFlags.None);
RenderTexture.active = renderTexture;
texture.ReadPixels(rect, 0, 0);
texture.Apply();
RenderTexture.active = null;
var data = texture.GetRawTextureData <byte>().ToArray();
UnityEngine.Object.Destroy(texture);
return(data);
}
else
{
Debug.Assert(channels == 1, "Can only handle a single channel RT.");
// Read pixels must be one of RGBA32, ARGB32, RGB24, RGBAFloat or RGBAHalf.
// So R16 and RFloat will be converted to RGBAFloat.
var texture = new Texture2D(renderTexture.width, renderTexture.height, TextureFormat.RGBAFloat, false);
RenderTexture.active = renderTexture;
texture.ReadPixels(rect, 0, 0);
texture.Apply();
RenderTexture.active = null;
var length = renderTexture.width * renderTexture.height;
var input = texture.GetRawTextureData <float>().ToArray();
UnityEngine.Object.Destroy(texture);
Array output = null;
int index = 0;
switch (channelSize)
{
case 2:
if (GraphicsFormatUtility.IsSignedFormat(renderTexture.graphicsFormat))
{
short[] shorts = ArrayUtilities.Allocate <short>(length);
var si = 0;
while (index < length)
{
shorts[index++] = (short)((float)short.MaxValue * input[si]);
si += 4;
}
output = shorts;
}
else
{
ushort[] ushorts = ArrayUtilities.Allocate <ushort>(length);
var si = 0;
while (index < length)
{
ushorts[index++] = (ushort)((float)ushort.MaxValue * input[si]);
si += 4;
}
output = ushorts;
}
break;
case 4:
float[] floats = ArrayUtilities.Allocate <float>(length);
var fi = 0;
while (index < length)
{
floats[index++] = input[fi];
fi += 4;
}
output = floats;
break;
default:
throw new NotSupportedException();
}
return(ArrayUtilities.Cast <byte>(output));
}
}
}