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public Rect GetTransparentBounds(BitmapSource source) {
var width = source.PixelWidth;
var height = source.PixelHeight;
var pixelBytes = new byte[height * width * 4];
source.CopyPixels(pixelBytes, width * 4, 0);
double? ax1 = null, ax2 = null, ay1 = null, ay2 = null;
Rect result = new Rect();
for (int y = 0; y < height; y++) {
for (int x = 0; x < width; x++) {
byte a = pixelBytes[(y * width + x) * 4 + 3];
if (a != 0xff) {
if (ax1.HasValue) {
ax1 = Math.Min(ax1.Value, x);
ax2 = Math.Max(ax2.Value, x);
} else {
ax1 = x;
ax2 = x;
}
if (ay1.HasValue) {
ay1 = Math.Min(ay1.Value, y);
ay2 = Math.Max(ay2.Value, y);
} else {
ay1 = y;
ay2 = y;
}
}
};
}
if(ax1.HasValue && ay1.HasValue){
result.X = ax1.Value;
result.Y = ay1.Value;
result.Width = ax2.Value - ax1.Value;
result.Height = ay2.Value - ay1.Value;
}
return result;
}