C# Crop white space from around the image

This code will crop the image based on all white and transparent pixels from around the image

public static Bitmap CropWhiteSpace(Bitmap bmp)
{
  int w = bmp.Width;
  int h = bmp.Height;
  int white = 0xffffff;
 
  Func allWhiteRow = r =>
  {
    for (int i = 0; i < w; ++i)
      if ((bmp.GetPixel(i, r).ToArgb() & white) != white)
        return false;
    return true;
  };
 
  Func 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);
  }
}

1. public static Bitmap CropWhiteSpace(Bitmap bmp)
2. {
3. int w = bmp.Width;
4. int h = bmp.Height;
5. int white = 0xffffff;
7. Func<int, bool=""> allWhiteRow = r =>
8. {
9. for (int i = 0; i < w; ++i)
10. if ((bmp.GetPixel(i, r).ToArgb() & white) != white)
11. return false;
12. return true;
13. };
15. Func<int, bool=""> allWhiteColumn = c =>
16. {
17. for (int i = 0; i < h; ++i)
18. if ((bmp.GetPixel(c, i).ToArgb() & white) != white)
19. return false;
20. return true;
21. };
23. int topmost = 0;
24. for (int row = 0; row < h; ++row)
25. {
26. if (!allWhiteRow(row))
27. break;
28. topmost = row;
29. }
31. int bottommost = 0;
32. for (int row = h - 1; row >= 0; --row)
33. {
34. if (!allWhiteRow(row))
35. break;
36. bottommost = row;
37. }
39. int leftmost = 0, rightmost = 0;
40. for (int col = 0; col < w; ++col)
41. {
42. if (!allWhiteColumn(col))
43. break;
44. leftmost = col;
45. }
47. for (int col = w - 1; col >= 0; --col)
48. {
49. if (!allWhiteColumn(col))
50. break;
51. rightmost = col;
52. }
54. if (rightmost == 0) rightmost = w; // As reached left
55. if (bottommost == 0) bottommost = h; // As reached top.
57. int croppedWidth = rightmost - leftmost;
58. int croppedHeight = bottommost - topmost;
60. if (croppedWidth == 0) // No border on left or right
61. {
62. leftmost = 0;
63. croppedWidth = w;
64. }
66. if (croppedHeight == 0) // No border on top or bottom
67. {
68. topmost = 0;
69. croppedHeight = h;
70. }
72. try
73. {
74. var target = new Bitmap(croppedWidth, croppedHeight);
75. using (Graphics g = Graphics.FromImage(target))
76. {
77. g.DrawImage(bmp,
78. new RectangleF(0, 0, croppedWidth, croppedHeight),
79. new RectangleF(leftmost, topmost, croppedWidth, croppedHeight),
80. GraphicsUnit.Pixel);
81. }
82. return target;
83. }
84. catch (Exception ex)
85. {
86. throw new Exception(
87. string.Format("Values are topmost={0} btm={1} left={2} right={3} croppedWidth={4} croppedHeight={5}", topmost, bottommost, leftmost, rightmost, croppedWidth, croppedHeight),
88. ex);
89. }
90. }
92. </int,></int,>

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);
  }
}

</int,></int,>

To test code you can try this

[Test]
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); 
}

1. [Test]
2. public void Test()
3. {
4. var inputPath = "image.png";
5. var outputPath = inputPath.Replace(".png", "-out.png");
7. var bitmap = new Bitmap(inputPath);
8. var cropped = CropWhiteSpace(bitmap);
9. cropped.Save(outputPath, ImageFormat.Png);
10. }

[Test]
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); 
}

OR in ASP.net as

using (Bitmap bitmap = new Bitmap(pngpath))
{
 using (MemoryStream ms = new MemoryStream())
 {
  var cropped = CropWhiteSpace(bitmap);
  cropped.Save(ms, System.Drawing.Imaging.ImageFormat.Png);
  ms.WriteTo(context.Response.OutputStream);
  //cropped.Save(outputPath, System.Drawing.Imaging.ImageFormat.Png); 

  //ms.WriteTo(context.Response.OutputStream);
 }
}

1. using (Bitmap bitmap = new Bitmap(pngpath))
2. {
3. using (MemoryStream ms = new MemoryStream())
4. {
5. var cropped = CropWhiteSpace(bitmap);
6. cropped.Save(ms, System.Drawing.Imaging.ImageFormat.Png);
7. ms.WriteTo(context.Response.OutputStream);
8. //cropped.Save(outputPath, System.Drawing.Imaging.ImageFormat.Png);
10. //ms.WriteTo(context.Response.OutputStream);
11. }
12. }

using (Bitmap bitmap = new Bitmap(pngpath))
{
 using (MemoryStream ms = new MemoryStream())
 {
  var cropped = CropWhiteSpace(bitmap);
  cropped.Save(ms, System.Drawing.Imaging.ImageFormat.Png);
  ms.WriteTo(context.Response.OutputStream);
  //cropped.Save(outputPath, System.Drawing.Imaging.ImageFormat.Png); 

  //ms.WriteTo(context.Response.OutputStream);
 }
}