/// <summary>
/// Function to convert the image data into a premultiplied format.
/// </summary>
/// <param name="baseImage">The image to convert.</param>
/// <returns>A <see cref="IGorgonImage"/> containing the image data with the premultiplied alpha pixel data.</returns>
/// <exception cref="ArgumentNullException">Thrown when the <paramref name="baseImage"/> is <b>null</b>.</exception>
/// <exception cref="ArgumentException">Thrown when image format is compressed.</exception>
/// <remarks>
/// <para>
/// Use this to convert an image to a premultiplied format. This takes each Red, Green and Blue element and multiplies them by the Alpha element.
/// </para>
/// <para>
/// If the image does not contain alpha then the method will return right away and no alterations to the image will be performed.
/// </para>
/// </remarks>
public static IGorgonImage ConvertToPremultipliedAlpha(this IGorgonImage baseImage)
{
IGorgonImage newImage = null;
GorgonNativeBuffer <byte> imageData = null;
if (baseImage == null)
{
throw new ArgumentNullException(nameof(baseImage));
}
if (!baseImage.FormatInfo.HasAlpha)
{
return(baseImage);
}
if (baseImage.FormatInfo.IsCompressed)
{
throw new ArgumentException(string.Format(Resources.GORIMG_ERR_FORMAT_NOT_SUPPORTED, baseImage.Format), nameof(baseImage));
}
try
{
var cloneImageInfo = new GorgonImageInfo(baseImage)
{
HasPreMultipliedAlpha = true
};
imageData = new GorgonNativeBuffer <byte>(baseImage.ImageData.Length);
baseImage.ImageData.CopyTo(imageData);
unsafe
{
newImage = new GorgonImage(cloneImageInfo, new GorgonReadOnlyPointer((void *)imageData, imageData.SizeInBytes));
int arrayOrDepth = newImage.ImageType == ImageType.Image3D ? newImage.Depth : newImage.ArrayCount;
for (int mip = 0; mip < newImage.MipCount; ++mip)
{
for (int i = 0; i < arrayOrDepth; ++i)
{
IGorgonImageBuffer buffer = newImage.Buffers[mip, i];
byte *ptr = (byte *)buffer.Data;
int rowPitch = buffer.PitchInformation.RowPitch;
for (int y = 0; y < buffer.Height; ++y)
{
ImageUtilities.SetPremultipliedScanline(ptr, rowPitch, ptr, rowPitch, buffer.Format);
ptr += rowPitch;
}
}
}
}
newImage.CopyTo(baseImage);
return(baseImage);
}
finally
{
imageData?.Dispose();
newImage?.Dispose();
}
}
