Cropping whitespace from image in C# [duplicate]

问题

Possible Duplicate:
Remove surrounding whitespace from an image

I'm looking for help to crop the whitespace on the top, bottom, left and right of an image.

I have found the following question/answer on SO, however the link with the answer is to a third party site, which does not appear to be up anymore.

回答1:

Found a solution here, but modified the return code section to allow for an empty image to be input, in which case the original image will be returned.

class ImageCrop
{
    public static byte[][] GetRGB(Bitmap bmp)
    {
        BitmapData bmp_data = bmp.LockBits(new Rectangle(0, 0, bmp.Width, bmp.Height), ImageLockMode.ReadOnly, PixelFormat.Format24bppRgb);
        IntPtr ptr = bmp_data.Scan0;
        int num_pixels = bmp.Width * bmp.Height, num_bytes = bmp_data.Stride * bmp.Height, padding = bmp_data.Stride - bmp.Width * 3, i = 0, ct = 1;
        byte[] r = new byte[num_pixels], g = new byte[num_pixels], b = new byte[num_pixels], rgb = new byte[num_bytes];
        System.Runtime.InteropServices.Marshal.Copy(ptr, rgb, 0, num_bytes);

        for (int x = 0; x < num_bytes - 3; x += 3)
        {
            if (x == (bmp_data.Stride * ct - padding)) { x += padding; ct++; };
            r[i] = rgb[x]; g[i] = rgb[x + 1]; b[i] = rgb[x + 2]; i++;
        }
        bmp.UnlockBits(bmp_data);
        return new byte[3][] { r, g, b };
    }
    public static Image AutoCrop(Bitmap bmp)
    {
        //Get an array containing the R,G,B components of each pixel
        var pixels = GetRGB(bmp);

        int h = bmp.Height - 1, w = bmp.Width, top = 0, bottom = h, left = bmp.Width, right = 0, white = 0;
        int tolerance = 95; // 95%

        bool prev_color = false;
        for (int i = 0; i < pixels[0].Length; i++)
        {
            int x = (i % (w)), y = (int)(Math.Floor((decimal)(i / w))), tol = 255 * tolerance / 100;
            if (pixels[0][i] >= tol && pixels[1][i] >= tol && pixels[2][i] >= tol) { white++; right = (x > right && white == 1) ? x : right; }
            else { left = (x < left && white >= 1) ? x : left; right = (x == w - 1 && white == 0) ? w - 1 : right; white = 0; }
            if (white == w) { top = (y - top < 3) ? y : top; bottom = (prev_color && x == w - 1 && y > top + 1) ? y : bottom; }
            left = (x == 0 && white == 0) ? 0 : left; bottom = (y == h && x == w - 1 && white != w && prev_color) ? h + 1 : bottom;
            if (x == w - 1) { prev_color = (white < w) ? true : false; white = 0; }
        }
        right = (right == 0) ? w : right; left = (left == w) ? 0 : left;

        //Crop the image
        if (bottom - top > 0)
        {
            Bitmap bmpCrop = bmp.Clone(new Rectangle(left, top, right - left + 1, bottom - top), bmp.PixelFormat);

            return (Bitmap)(bmpCrop);
        }
        else
        {
            return bmp;
        }
    }


}

来源：https://stackoverflow.com/questions/8057380/cropping-whitespace-from-image-in-c-sharp

标签

image

crop