从图像中删除周围的空白

Question

我有一块从客户那里收到的产品图片。每个产品图像是一个东西的图片，它是用白色背景拍摄的。我想裁剪图像的所有周围部分，但只留下产品在中间。这可能吗？

举个例子：[http://www.5dnet.de/media/catalog/product/d/r/dress_shoes_5.jpg][1]

我不希望删除所有白色像素，但我确实想要裁剪图像，以便最顶部的像素行包含一个非白色像素，最左边的垂直像素行包含一个非白色像素，最底部的水平像素行包含一个非白色像素等。

C＃或VB.net中的代码将不胜感激。

Answer 1

我发现我必须调整Dmitri的答案，以确保它适用于实际上不需要裁剪的图像（水平，垂直或两者）...

    public static Bitmap Crop(Bitmap bmp)
    {
        int w = bmp.Width;
        int h = bmp.Height;

        Func<int, bool> allWhiteRow = row =>
        {
            for (int i = 0; i < w; ++i)
                if (bmp.GetPixel(i, row).R != 255)
                    return false;
            return true;
        };

        Func<int, bool> allWhiteColumn = col =>
        {
            for (int i = 0; i < h; ++i)
                if (bmp.GetPixel(col, i).R != 255)
                    return false;
            return true;
        };

        int topmost = 0;
        for (int row = 0; row < h; ++row)
        {
            if (allWhiteRow(row))
                topmost = row;
            else break;
        }

        int bottommost = 0;
        for (int row = h - 1; row >= 0; --row)
        {
            if (allWhiteRow(row))
                bottommost = row;
            else break;
        }

        int leftmost = 0, rightmost = 0;
        for (int col = 0; col < w; ++col)
        {
            if (allWhiteColumn(col))
                leftmost = col;
            else
                break;
        }

        for (int col = w - 1; col >= 0; --col)
        {
            if (allWhiteColumn(col))
                rightmost = col;
            else
                break;
        }

        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);
        }
    }

Answer 2

这是我（相当冗长）的解决方案：

public Bitmap Crop(Bitmap bmp)
{
  int w = bmp.Width, h = bmp.Height;

  Func<int, bool> allWhiteRow = row =>
  {
    for (int i = 0; i < w; ++i)
      if (bmp.GetPixel(i, row).R != 255)
        return false;
    return true;
  };

  Func<int, bool> allWhiteColumn = col =>
  {
    for (int i = 0; i < h; ++i)
      if (bmp.GetPixel(col, i).R != 255)
        return false;
    return true;
  };

  int topmost = 0;
  for (int row = 0; row < h; ++row)
  {
    if (allWhiteRow(row))
      topmost = row;
    else break;
  }

  int bottommost = 0;
  for (int row = h - 1; row >= 0; --row)
  {
    if (allWhiteRow(row))
      bottommost = row;
    else break;
  }

  int leftmost = 0, rightmost = 0;
  for (int col = 0; col < w; ++col)
  {
    if (allWhiteColumn(col))
      leftmost = col;
    else
      break;
  }

  for (int col = w-1; col >= 0; --col)
  {
    if (allWhiteColumn(col))
      rightmost = col;
    else
      break;
  }

  int croppedWidth = rightmost - leftmost;
  int croppedHeight = bottommost - topmost;
  try
  {
    Bitmap 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}", topmost, bottommost, leftmost, rightmost),
      ex);
  }
}

Answer 3

我需要一个适用于大图像的解决方案（GetPixel很慢），所以我在下面编写了扩展方法。它似乎在我的有限测试中运作良好。缺点是＆＃34;允许不安全代码＆＃34;必须在您的项目中进行检查。

public static Image AutoCrop(this Bitmap bmp)
{
    if (Image.GetPixelFormatSize(bmp.PixelFormat) != 32)
        throw new InvalidOperationException("Autocrop currently only supports 32 bits per pixel images.");

    // Initialize variables
    var cropColor = Color.White;

    var bottom = 0;
    var left = bmp.Width; // Set the left crop point to the width so that the logic below will set the left value to the first non crop color pixel it comes across.
    var right = 0;
    var top = bmp.Height; // Set the top crop point to the height so that the logic below will set the top value to the first non crop color pixel it comes across.

    var bmpData = bmp.LockBits(new Rectangle(0, 0, bmp.Width, bmp.Height), ImageLockMode.ReadOnly, bmp.PixelFormat);

    unsafe
    {
        var dataPtr = (byte*)bmpData.Scan0;

        for (var y = 0; y < bmp.Height; y++)
        {
            for (var x = 0; x < bmp.Width; x++)
            {
                var rgbPtr = dataPtr + (x * 4);

                var b = rgbPtr[0];
                var g = rgbPtr[1];
                var r = rgbPtr[2];
                var a = rgbPtr[3];

                // If any of the pixel RGBA values don't match and the crop color is not transparent, or if the crop color is transparent and the pixel A value is not transparent
                if ((cropColor.A > 0 && (b != cropColor.B || g != cropColor.G || r != cropColor.R || a != cropColor.A)) || (cropColor.A == 0 && a != 0))
                {
                    if (x < left)
                        left = x;

                    if (x >= right)
                        right = x + 1;

                    if (y < top)
                        top = y;

                    if (y >= bottom)
                        bottom = y + 1;
                }
            }

            dataPtr += bmpData.Stride;
        }
    }

    bmp.UnlockBits(bmpData);

    if (left < right && top < bottom)
        return bmp.Clone(new Rectangle(left, top, right - left, bottom - top), bmp.PixelFormat);

    return null; // Entire image should be cropped, so just return null
}

Answer 4

我自己编写代码来实现这一点 - 让基础知识变得不是很难。

基本上，您需要扫描像素行/列以检查非白色像素并隔离产品图像的边界，然后创建一个仅包含该区域的新位图。

请注意，虽然Bitmap.GetPixel()方法有效，但速度相对较慢。如果处理时间很重要，则需要使用Bitmap.LockBits()将位图锁定在内存中，然后在unsafe { }块内使用一些简单的指针直接访问像素。

CodeProject上的

This article提供了一些您可能会觉得有用的更多细节。

Answer 5

这当然是可能的。在伪代码中：

topmost = 0
for row from 0 to numRows:
    if allWhiteRow(row): 
        topmost = row
    else:
        # found first non-white row from top
        break

botmost = 0
for row from numRows-1 to 0:
    if allWhiteRow(row): 
        botmost = row
    else:
        # found first non-white row from bottom
        break

左右同样如此。

allWhiteRow的代码会涉及查看该行中的像素并确保它们全部关闭为255,255,255。

Answer 6

在顶部和左侧修复剩余的1px空白区域

    public Bitmap Crop(Bitmap bitmap)
    {
        int w = bitmap.Width;
        int h = bitmap.Height;

        Func<int, bool> IsAllWhiteRow = row =>
        {
            for (int i = 0; i < w; i++)
            {
                if (bitmap.GetPixel(i, row).R != 255)
                {
                    return false;
                }
            }
            return true;
        };

        Func<int, bool> IsAllWhiteColumn = col =>
        {
            for (int i = 0; i < h; i++)
            {
                if (bitmap.GetPixel(col, i).R != 255)
                {
                    return false;
                }
            }
            return true;
        };

        int leftMost = 0;
        for (int col = 0; col < w; col++)
        {
            if (IsAllWhiteColumn(col)) leftMost = col + 1;
            else break;
        }

        int rightMost = w - 1;
        for (int col = rightMost; col > 0; col--)
        {
            if (IsAllWhiteColumn(col)) rightMost = col - 1;
            else break;
        }

        int topMost = 0;
        for (int row = 0; row < h; row++)
        {
            if (IsAllWhiteRow(row)) topMost = row + 1;
            else break;
        }

        int bottomMost = h - 1;
        for (int row = bottomMost; row > 0; row--)
        {
            if (IsAllWhiteRow(row)) bottomMost = row - 1;
            else break;
        }

        if (rightMost == 0 && bottomMost == 0 && leftMost == w && topMost == h)
        {
            return bitmap;
        }

        int croppedWidth = rightMost - leftMost + 1;
        int croppedHeight = bottomMost - topMost + 1;

        try
        {
            Bitmap target = new Bitmap(croppedWidth, croppedHeight);
            using (Graphics g = Graphics.FromImage(target))
            {
                g.DrawImage(bitmap,
                    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 top={0} bottom={1} left={2} right={3}", topMost, bottomMost, leftMost, rightMost), ex);
        }
    }

Answer 7

pnmcrop图形实用程序库中的netpbm实用程序就是这样做的。

我建议查看他们的代码，可从http://netpbm.sourceforge.net/

获取

Answer 8

public void TrimImage() {
    int threshhold = 250;


    int topOffset = 0;
    int bottomOffset = 0;
    int leftOffset = 0;
    int rightOffset = 0;
    Bitmap img = new Bitmap(@"e:\Temp\Trim_Blank_Image.png");


    bool foundColor = false;
    // Get left bounds to crop
    for (int x = 1; x < img.Width && foundColor == false; x++)
    {
        for (int y = 1; y < img.Height && foundColor == false; y++)
        {
            Color color = img.GetPixel(x, y);
            if (color.R < threshhold || color.G < threshhold || color.B < threshhold)
                foundColor = true;
        }
        leftOffset += 1;
    }


    foundColor = false;
    // Get top bounds to crop
    for (int y = 1; y < img.Height && foundColor == false; y++)
    {
        for (int x = 1; x < img.Width && foundColor == false; x++)
        {
            Color color = img.GetPixel(x, y);
            if (color.R < threshhold || color.G < threshhold || color.B < threshhold)
                foundColor = true;
        }
        topOffset += 1;
    }


    foundColor = false;
    // Get right bounds to crop
    for (int x = img.Width - 1; x >= 1 && foundColor == false; x--)
    {
        for (int y = 1; y < img.Height && foundColor == false; y++)
        {
            Color color = img.GetPixel(x, y);
            if (color.R < threshhold || color.G < threshhold || color.B < threshhold)
                foundColor = true;
        }
        rightOffset += 1;
    }


    foundColor = false;
    // Get bottom bounds to crop
    for (int y = img.Height - 1; y >= 1 && foundColor == false; y--)
    {
        for (int x = 1; x < img.Width && foundColor == false; x++)
        {
            Color color = img.GetPixel(x, y);
            if (color.R < threshhold || color.G < threshhold || color.B < threshhold)
                foundColor = true;
        }
        bottomOffset += 1;
    }


    // Create a new image set to the size of the original minus the white space
    //Bitmap newImg = new Bitmap(img.Width - leftOffset - rightOffset, img.Height - topOffset - bottomOffset);

    Bitmap croppedBitmap = new Bitmap(img);
    croppedBitmap = croppedBitmap.Clone(
                    new Rectangle(leftOffset - 3, topOffset - 3, img.Width - leftOffset - rightOffset + 6, img.Height - topOffset - bottomOffset + 6),
                    System.Drawing.Imaging.PixelFormat.DontCare);


    // Get a graphics object for the new bitmap, and draw the original bitmap onto it, offsetting it do remove the whitespace
    //Graphics g = Graphics.FromImage(croppedBitmap);
    //g.DrawImage(img, 1 - leftOffset, 1 - rightOffset);
    croppedBitmap.Save(@"e:\Temp\Trim_Blank_Image-crop.png", ImageFormat.Png);
}

我从ms的其他帖子中获得了代码，但是有 bug ，我已经更改了一些内容，现在可以正常使用了。

http://msm2020-sc.blogspot.com/2013/07/c-crop-white-space-from-around-image.html上的帖子