public static Bgra32ImageBuffer ReadImageBuffer(this OpenSlideImage image, int level, long x, long y, long w, long h)
{
var buffer = new Bgra32ImageBuffer(checked ((int)w), checked ((int)h));
image.ReadRegion(level, x, y, w, h, ref buffer.GetPinnableReference());
return(buffer);
}
private static Image <Bgra32> GenerateThumbnail(OpenSlideImage image, int maxWidth, int maxHeight)
{
if (image == null)
{
throw new ArgumentNullException(nameof(image));
}
(long width, long height) = image.Dimensions;
// 决定合适的level
double downsampleWidth = width / (double)maxWidth;
double downsampleHeight = height / (double)maxHeight;
double downsample = Math.Max(downsampleWidth, downsampleHeight);
int level = image.GetBestLevelForDownsample(downsample);
(long levelWidth, long levelHeight) = image.GetLevelDimensions(level);
// 计算目标大小
int targetWidth, targetHeight;
if (downsampleWidth > downsampleHeight)
{
// width缩小较大，将maxWidth作为标准
targetWidth = maxWidth;
targetHeight = (int)(height / downsampleWidth);
}
else
{
// height缩小较大，将maxHeight作为标准
targetWidth = (int)(width / downsampleHeight);
targetHeight = maxHeight;
}
Image <Bgra32> output;
checked
{
output = new Image <Bgra32>((int)levelWidth, (int)levelHeight);
}
image.ReadRegion(
level, 0, 0, levelWidth, levelHeight,
ref Unsafe.As <Bgra32, byte>(ref MemoryMarshal.GetReference(output.GetPixelSpan())));
output.Mutate(ctx =>
{
ctx.Resize(targetWidth, targetHeight);
});
return(output);
}