我有一個我們從客戶收到的產品圖像塊。每個產品圖片都是一些東西的圖片，並且是以白色背景拍攝的。我想裁剪圖像的所有周圍部分，但只留下中間的產品。這可能嗎？從圖像中刪除周圍的空白
舉個例子：http://www.5dnet.de/media/catalog/product/d/r/dress_shoes_5.jpg][1]
我不希望所有白色像素去掉，但是我想要的圖像裁剪，使像素的最頂層的行包含一個非白色像素，左大多數垂直像素行包含一個非白色像素，最底部水平行像素包含一個非白色像素等。
C＃或VB.net中的代碼將不勝感激。
我已經編寫了自己的代碼來完成這個任務 - 基礎知識不會太困難。
基本上，您需要掃描像素行/列以檢查非白色像素，並隔離產品圖像的邊界，然後創建一個僅包含該區域的新位圖。
請注意，儘管Bitmap.GetPixel()方法有效，但速度相對較慢。如果處理時間很重要，則需要使用Bitmap.LockBits()來鎖定內存中的位圖，然後使用unsafe { }塊中的一些簡單指針直接訪問像素。
This article CodeProject給出了一些您可能會覺得有用的細節。
這當然有可能。在僞代碼中：
![http://www.5dnet.de/media/catalog/product/d/r/dress_shoes_5.jpg][1]](http://www.5dnet.de/media/catalog/product/d/r/dress_shoes_5.jpg][1]){kind=link}
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
對於左和右類似。
allWhiteRow的代碼將涉及查看該行中的像素，並確保它們都是關閉至255,255,255。
來自netpbm圖形實用程序庫的pnmcrop實用程序正是如此。
我建議在看他們的代碼，可以從http://netpbm.sourceforge.net/
這是我（相當長的）解決方案：
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);
}
}
完美的作品，除非croppedWidth或croppedHeight爲零，在這種情況下，我分別將它們設置爲bmp.Width或bmp.Height，它的作用就像一個魅力:) – 2011-12-25 14:23:59
這是否適合每種圖像？像PNG JPEG或GIF？ – MonsterMMORPG 2016-06-29 11:50:55
我發現我不得不調整德米特里的答案，以確保它的工作原理與圖片，唐」實際上需要裁剪（水平，垂直或兩者）...
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);
}
}
我需要一個解決方案，處理大圖像（GetPixel是slo w），所以我寫了下面的擴展方法。這似乎在我有限的測試中運行良好。缺點是必須在項目中檢查「允許不安全代碼」。
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
}
固定在頂部剩餘1px的空白和左
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);
}
}
這是不是花太多時間爲1000×1000一圖像處理？請指教。 – techno 2016-02-20 10:45:56
取決於你的「太多時間」的定義 - 這取決於你的上下文。我建議使用`Bitmap.GetPixel（）`編寫代碼，然後對結果進行基準測試以查看。另請注意，智能算法比個別像素讀取的微優化更重要。 – Bevan 2016-02-24 02:10:13