public static Bitmap CropWhiteSpace(Bitmap bmp)
{
int w = bmp.Width;
int h = bmp.Height;
int white = 0xffffff;
Func<int, bool> allWhiteRow = r =>
{
for (int i = 0; i < w; ++i)
if ((bmp.GetPixel(i, r).ToArgb() & white) != white)
return false;
return true;
};
Func<int, bool> allWhiteColumn = c =>
{
for (int i = 0; i < h; ++i)
if ((bmp.GetPixel(c, i).ToArgb() & white) != white)
return false;
return true;
};
int topmost = 0;
for (int row = 0; row < h; ++row)
{
if (!allWhiteRow(row))
break;
topmost = row;
}
int bottommost = 0;
for (int row = h - 1; row >= 0; --row)
{
if (!allWhiteRow(row))
break;
bottommost = row;
}
int leftmost = 0, rightmost = 0;
for (int col = 0; col < w; ++col)
{
if (!allWhiteColumn(col))
break;
leftmost = col;
}
for (int col = w - 1; col >= 0; --col)
{
if (!allWhiteColumn(col))
break;
rightmost = col;
}
if (rightmost == 0) rightmost = w; // As reached left
if (bottommost == 0) bottommost = h; // As reached top.
int croppedWidth = rightmost - leftmost;
int croppedHeight = bottommost - topmost;
if (croppedWidth == 0) // No border on left or right
{
leftmost = 0;
croppedWidth = w;
}
if (croppedHeight == 0) // No border on top or bottom
{
topmost = 0;
croppedHeight = h;
}
try
{
var target = new Bitmap(croppedWidth, croppedHeight);
using (Graphics g = Graphics.FromImage(target))
{
g.DrawImage(bmp,
new RectangleF(0, 0, croppedWidth, croppedHeight),
new RectangleF(leftmost, topmost, croppedWidth, croppedHeight),
GraphicsUnit.Pixel);
}
return target;
}
catch (Exception ex)
{
throw new Exception(
string.Format("Values are topmost={0} btm={1} left={2} right={3} croppedWidth={4} croppedHeight={5}", topmost, bottommost, leftmost, rightmost, croppedWidth, croppedHeight),
ex);
}
}
public void Test()
{
var inputPath = "image.png";
var outputPath = inputPath.Replace(".png", "-out.png");
var bitmap = new Bitmap(inputPath);
var cropped = CropWhiteSpace(bitmap);
cropped.Save(outputPath, ImageFormat.Png);
}
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