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This article mainly explains "how to achieve Bitmap image processing acceleration in C#", the content of the explanation is simple and clear, easy to learn and understand, the following please follow the editor's ideas slowly in depth, together to study and learn "how to achieve Bitmap image processing acceleration in C#" it!

BitmapData class

The BitmapData class is dedicated to bitmap processing. Unlike Bitmap, it uses pointers to modify memory directly, while Bitmap uses the SetPixel () method to modify colors indirectly, so it is much more efficient than SetPixel ().

Traditional code

Taking grayscale processing as an example, in order to facilitate the demonstration, the grayscale algorithm here is Gray= (R+G+B) / 3.

Private void Gray_Tradition () {for (int I = 0; I)

< bitmap.Width; i++) { for(int j = 0; j < bitmap.Height; j++) { Color color = bitmap.GetPixel(i, j); int RGB = (color.R + color.G + color.B) / 3; bitmap.SetPixel(i, j, Color.FromArgb(255, RGB, RGB, RGB)); } }}使用BitmapData的代码private void Gray_BitmapData(){ int width = bitmap.Width, height = bitmap.Height;//图片的宽度和高度 //在内存中以读写模式锁定Bitmap BitmapData bitmapData = bitmap.LockBits( new Rectangle(0, 0, width, height), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb); //图片像素点数组的长度，由于一个像素点占了3个字节，所以要乘上3 int size = width * height * 3; //缓冲区数组 byte[] srcArray = new byte[size]; //获取第一个像素的地址 IntPtr ptr = bitmapData.Scan0; //把像素值复制到缓冲区 Marshal.Copy(ptr, srcArray, 0, size); int p; for (int i = 0; i < width; i++) { for (int j = 0; j < height; j++) { //定位像素点位置 p = j * width * 3 + i * 3; //计算灰度值 byte color = (byte)((srcArray[p] + srcArray[p + 1] + srcArray[p + 2]) / 3); srcArray[p] = srcArray[p + 1] = srcArray[p + 2] = color; } } //从缓冲区复制回BitmapData Marshal.Copy(srcArray, 0, ptr, size); //从内存中解锁 bitmap.UnlockBits(bitmapData);}效率对比代码private void onTest(){ double t1, t2; Stopwatch watch = new Stopwatch(); watch.Start(); Gray_BitmapData(); watch.Stop(); t1 = watch.Elapsed.TotalMilliseconds; watch.Reset(); watch.Start(); Gray_Tradition(); watch.Stop(); t2 = watch.Elapsed.TotalMilliseconds; MessageBox.Show("BitmapData=" + (long)t1 + "\nTradition=" + (long)t2);} 图片信息 耗时

You can see that the traditional method takes 106 times more time than the BitmapData method, which takes a full 14 seconds, while BitmapData only takes 0.1 seconds.

GPU acceleration

After using CUDA to generate dll, you can process images efficiently on GPU, but this method requires the use of dll and is extremely tedious, so it is only suitable for use when there is a very high demand for efficiency.

Generate Dll#include "cuda_runtime.h" # include "device_launch_parameters.h" # include # include _ global__ void DoInKernel (byte* o, int num) {int I = blockIdx.x * blockDim.x + threadIdx.x; if (I > = num) return; byte* ori = o + I * 3; ori [0] = ori [1] = ori [2] = (ori [0] + ori [1] + ori [2]) / 3 } extern "C" _ declspec (dllexport) void Gray (byte* oriArray, int num) {int size = num * 3 * sizeof (byte); byte* dev_ori; / / allocate memory cudaMalloc ((void**) & dev_ori, size) on GPU; / / copy the array to cudaMemcpy (dev_ori, oriArray, size, cudaMemcpyHostToDevice); / / Compute DoInKernel > (dev_ori, num) / / copy from video memory to memory cudaMemcpy (oriArray, dev_ori, size, cudaMemcpyDeviceToHost); / / release cudaFree (dev_ori);}

In fact, the number of thread and block of GPU should be dynamically adjusted according to the actual array size, but for demonstration purposes, 1024 threads are defined directly.

Call DllDllImport ("CUDA.dll", EntryPoint = "Gray", CallingConvention = CallingConvention.Cdecl)] public static extern void Gray (IntPtr ori, int num)

At this point, there is no need to define a buffer array, you can directly copy the data to the video memory to use

Private void Gray_GPU () {int width = bitmap.Width, height = bitmap.Height;// width and height of the picture / / Lock Bitmap BitmapData bitmapData = bitmap.LockBits (new Rectangle (0,0, width, height), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb) in read-write mode in memory; / / the length of the pixel array of the picture, multiplied by 3 int size = width * height * 3 because one pixel takes up 3 bytes / / get the address of the first pixel IntPtr ptr = bitmapData.Scan0; Gray (ptr, width * height); / / unlock bitmap.UnlockBits (bitmapData) from memory; pictureBox1.Refresh ();} time-consuming

Since it takes time to load dll, the second execution time is the real GPU execution time.

It only took 34 milliseconds

Thank you for your reading, the above is the content of "how to achieve Bitmap image processing acceleration in C#". After the study of this article, I believe you have a deeper understanding of how to achieve Bitmap image processing acceleration in C#. The specific use of the situation also needs to be verified in practice. Here is, the editor will push for you more related knowledge points of the article, welcome to follow!

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