使用lockbits方法从C＃中的图像中提取颜色。 [英] Extracting color from image in C# using lockbits method.

问题描述

我想从图像中提取蓝色，我为它编写了代码。我在C＃中使用lockbits方法。

24位图像 - BGR

[0] =蓝色

[1] =绿色
[2] =红色

这是代码 -

I want to extract blue color from image, I wrote code for it. I am using lockbits method in C#.
24 bit image - BGR
[0] = Blue
[1] = Green
[2] = Red
Here is code -

BitmapData bitmapdata = bitmap.LockBits (
                            new Rectangle(
                                0,
                                0,
                                bitmap.Width,
                                bitmap.Height),
                            ImageLockMode.ReadWrite,
                            PixelFormat.Format24bppRgb );
IntPtr                  ptr = bitmapdata.Scan0;
                                     // declare  an array to hold
                                     // the bytes of bitmap
int                     bytes = Math.Abs ( bitmapdata.Stride ) *
                                bitmap.Height;
byte [ ]                values = new byte [ bytes ];

System.Runtime.InteropServices.Marshal.Copy ( ptr, values, 0, bytes );

for ( int i = 0; ( i < values.Length ); i += 3 )
    {
                                     // Comparing blue and green and
                                     // blue and red. if blue is greater
                                     // than both pixel than make it
                                     // more intensive otherwise make white
    if ( ( values [ i ] - values [ i + 1 ] > 9 ) &&
         ( values [ i ] - values [ i + 2 ] > 9 )
        {
        values [ i ] = 255;
        values [ i + 1 ] = 0;
        values [ i + 2 ] = 0;
        }
    else
        {
        values [ i ] =  255;
        values [ i + 1 ] =  255;
        values [ i + 2 ] =   255;
        }
    }
bitmap.Save("bitmap.jpg");

此代码工作正常但在一张图片中我遇到了问题，当图像没有颜色时，它会提取红色而不是蓝色。

运行此代码时，此图像应为白色。

我不想使用getpixel或setpixel方法。

附图像。

This code is working fine but in one image I got problem, it was extracting red color instead of blue when the image has no color.
This image should be white when I run this code.
I don't want to use getpixel or setpixel method.
Image attached.

推荐答案

它只是意味着其中一个图像恰好具有不同的像素格式。不同的格式会产生不同的内存布局。您必须阅读该文件，然后阅读属性 PixelFormat ：

https://msdn.microsoft.com/en-us/library/system.drawing.image.pixelformat（v = VS .110）.aspx [ ^ ]，

https://msdn.microsoft.com/en-us/library/system.drawing.imaging.pixelformat%28v=vs.110%29.aspx [ ^ ]。



阅读给定像素格式的描述并调整您的假设内存布局。

-SA

It simply means that one of the images happens to have different pixel format. Different formats makes different memory layouts. You have to read the file and then read the property PixelFormat:
https://msdn.microsoft.com/en-us/library/system.drawing.image.pixelformat(v=vs.110).aspx[^],
https://msdn.microsoft.com/en-us/library/system.drawing.imaging.pixelformat%28v=vs.110%29.aspx[^].

Read the description on the given pixel format and adjust your assumed memory layout.

—SA

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