上兩節(jié)課都是對(duì)一個(gè)數(shù)組進(jìn)行處理。這節(jié)我們來(lái)個(gè)有意思的。同樣是旋轉(zhuǎn)。但我們旋轉(zhuǎn)的對(duì)象是張（２５６*２５６）的圖片。圖片旋轉(zhuǎn)４５度，旋轉(zhuǎn)后大小還是２５６*２５６，超出部份進(jìn)行剪除。

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圖片旋轉(zhuǎn)處理有個(gè)特別的地方。buf_A是存儲(chǔ)源圖數(shù)據(jù)（R,G,B顏色分量）,buf_B是存儲(chǔ)旋轉(zhuǎn)后數(shù)據(jù)。我們不能簡(jiǎn)單將buf_A中的數(shù)據(jù)直接計(jì)算旋轉(zhuǎn)后位置。而是遍歷buf_B每個(gè)數(shù)據(jù)，計(jì)算那些數(shù)據(jù)旋轉(zhuǎn)后存在這個(gè)位置的數(shù)據(jù)他在buf_A的坐標(biāo)是多少。為什么呢？不是因?yàn)椴荒苤苯有D(zhuǎn)。而是因?yàn)樽鴺?biāo)是整數(shù)型。進(jìn)行旋轉(zhuǎn)計(jì)算后會(huì)得出浮點(diǎn)數(shù)，有小數(shù)。計(jì)算精度不同。如果還用直接旋轉(zhuǎn)計(jì)算方法。成出的位圖將會(huì)出現(xiàn)斑點(diǎn)。大家可試下。

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我們來(lái)看源碼

rotate.cl源碼

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__kernel void rotation(__global int* A, ????????????????????__global int* B, ????????????????????int width, ????????????????????int height, ????????????????????float sinangle, ????????????????????float cosangle) { ????//獲取索引號(hào)，這里是二維的，所以可以取兩個(gè) ????//否則另一個(gè)永遠(yuǎn)是0 ????int col = get_global_id(0); ????int row = get_global_id(1); ????//計(jì)算圖形中心點(diǎn) ????float cx = ((float)width)/2; ????float cy = ((float)height)/2; ????int nx = (int)(cx + cosangle * ((float)col-cx) + sinangle * ((float)row-cy)); ????int ny = (int)(cy + (-1*sinangle) * ((float)col-cx) + cosangle * ((float)row-cy)); ????//邊界檢測(cè) ????if(nx>=0 && nx<width && ny>=0 && ny<height) ????{ ????????B[col*3+0+row*width*3] = A[nx*3+0+ny*width*3]; ????????B[col*3+1+row*width*3] = A[nx*3+1+ny*width*3]; ????????B[col*3+2+row*width*3] = A[nx*3+2+ny*width*3]; ????} }

main.cpp源碼

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#include <iostream> #include <stdio.h> #include <string.h> #include <string> #include <conio.h> #include <math.h>//數(shù)學(xué)庫(kù) #include <CL/cl.h>//包含CL的頭文件 //調(diào)用freeimage #include <freeimage.h> using namespace std; //8x8數(shù)組 const int dim_x = 256; const int dim_y = 256; //45度的弧度 const float angle = 3.1415926f/4.0f; static int buf_A[dim_x*dim_y*3]; static int buf_B[dim_x*dim_y*3]; //加載圖片 //以RGBA格式存儲(chǔ)圖片 static bool LoadImg(const char* fname) { ????//初始化FreeImage ????FreeImage_Initialise(TRUE); ????//定義圖片格式為未知 ????FREE_IMAGE_FORMAT fif = FIF_UNKNOWN; ????//獲取圖片格式 ????fif = FreeImage_GetFileType(fname,0); ????//根據(jù)獲取格式讀取圖片數(shù)據(jù) ????FIBITMAP* bitmap = FreeImage_Load(fif,fname,0); ????if(!bitmap) ????{ ????????printf("load error!\n"); ????????return false; ????} ????int x,y; ????RGBQUAD m_rgb; ????//獲取圖片長(zhǎng)寬 ????int width = (int)FreeImage_GetWidth(bitmap); ????int height = (int)FreeImage_GetHeight(bitmap); ????//獲取圖片數(shù)據(jù) ????//按RGBA格式保存到數(shù)組中 ????for(y=0;y<height;y++) ????{ ????????for(x=0;x<width;x++) ????????{ ????????????//獲取像素值 ????????????FreeImage_GetPixelColor(bitmap,x,y,&m_rgb); ????????????//將RGB值存入數(shù)組 ????????????buf_A[y*width*3+x*3+2] = m_rgb.rgbRed; ????????????buf_A[y*width*3+x*3+1] = m_rgb.rgbGreen; ????????????buf_A[y*width*3+x*3+0] = m_rgb.rgbBlue; ????????} ????} ????FreeImage_Unload(bitmap); ????return true; } static bool SaveImg() { ????//初始化FreeImage ????FreeImage_Initialise(TRUE); ????FIBITMAP* bitmap =FreeImage_Allocate(dim_x,dim_y,32,8,8,8); ????int m,n; ????for(n=0;n<dim_y;n++) ????{ ????????BYTE *bits =FreeImage_GetScanLine(bitmap,n); ????????for(m=0;m<dim_x;m++) ????????{ ????????????bits[0] = buf_B[dim_x*3*n+m*3+0]; ????????????bits[1] = buf_B[dim_x*3*n+m*3+1]; ????????????bits[2] = buf_B[dim_x*3*n+m*3+2]; ????????????bits[3] = 255; ????????????bits+=4; ????????} ????} ????//保存圖片為PNG格式 ????if(false ==FreeImage_Save(FIF_PNG, bitmap,"rotate.png", PNG_DEFAULT)) ????{ ????????printf("save image error\n"); ????} ????FreeImage_Unload(bitmap); ????return true; } //從外部文件獲取cl內(nèi)核代碼 bool GetFileData(const char* fname,string& str) { ????FILE* fp = fopen(fname,"r"); ????if(fp==NULL) ????{ ????????printf("no found file\n"); ????????return false; ????} ????while(feof(fp)==0) ????{ ????????str += fgetc(fp); ????} ????return true; } int main() { ????if(LoadImg("bk.png")==false) ????{ ????????printf("error load bk.png!\n"); ????????return 0; ????} ????//先讀外部CL核心代碼，如果失敗則退出。 ????//代碼存buf_code里面 ????string code_file; ????if(false == GetFileData("rotate.cl",code_file)) ????{ ????????printf("Open rotate.cl error\n"); ????????return 0; ????} ????char* buf_code = new char[code_file.size()]; ????strcpy(buf_code,code_file.c_str()); ????buf_code[code_file.size()-1] = NULL; ????//聲明CL所需變量。 ????cl_device_id device; ????cl_platform_id platform_id = NULL; ????cl_context context; ????cl_command_queue cmdQueue; ????cl_mem bufferA,bufferB; ????cl_program program; ????cl_kernel kernel = NULL; ????//我們使用的是二維向量 ????//設(shè)定向量大小（維數(shù)） ????size_t globalWorkSize[2]; ????globalWorkSize[0] = dim_x; ????globalWorkSize[1] = dim_y; ????cl_int err; ????/* ????????定義輸入變量和輸出變量，并設(shè)定初值 ????*/ ????size_t datasize = sizeof(int) * dim_x * dim_y * 3; ????//step 1:初始化OpenCL ????err = clGetPlatformIDs(1,&platform_id,NULL); ????if(err!=CL_SUCCESS) ????{ ????????cout<<"clGetPlatformIDs error:"<<err<<endl; ????????return 0; ????} ????//這次我們只用CPU來(lái)進(jìn)行并行運(yùn)算，當(dāng)然你也可以該成GPU ????clGetDeviceIDs(platform_id,CL_DEVICE_TYPE_CPU,1,&device,NULL); ????//step 2:創(chuàng)建上下文 ????context = clCreateContext(NULL,1,&device,NULL,NULL,NULL); ????//step 3:創(chuàng)建命令隊(duì)列 ????cmdQueue = clCreateCommandQueue(context,device,0,NULL); ????//step 4:創(chuàng)建數(shù)據(jù)緩沖區(qū) ????bufferA = clCreateBuffer(context, ?????????????????????????????CL_MEM_READ_ONLY, ?????????????????????????????datasize,NULL,NULL); ????bufferB = clCreateBuffer(context, ?????????????????????????????CL_MEM_WRITE_ONLY, ?????????????????????????????datasize,NULL,NULL); ????//step 5:將數(shù)據(jù)上傳到緩沖區(qū) ????clEnqueueWriteBuffer(cmdQueue, ?????????????????????????bufferA,CL_FALSE, ?????????????????????????0,datasize, ?????????????????????????buf_A,0, ?????????????????????????NULL,NULL); ????//step 6:加載編譯代碼,創(chuàng)建內(nèi)核調(diào)用函數(shù) ????program = clCreateProgramWithSource(context,1, ????????????????????????????????????????(const char**)&buf_code, ????????????????????????????????????????NULL,NULL); ????clBuildProgram(program,1,&device,NULL,NULL,NULL); ????kernel = clCreateKernel(program,"rotation",NULL); ????//step 7:設(shè)置參數(shù)，執(zhí)行內(nèi)核 ????float sinangle = sinf(angle); ????float cosangle = cosf(angle); ????clSetKernelArg(kernel,0,sizeof(cl_mem),&bufferA); ????clSetKernelArg(kernel,1,sizeof(cl_mem),&bufferB); ????clSetKernelArg(kernel,2,sizeof(cl_int),&dim_x); ????clSetKernelArg(kernel,3,sizeof(cl_int),&dim_y); ????clSetKernelArg(kernel,4,sizeof(cl_float),&sinangle); ????clSetKernelArg(kernel,5,sizeof(cl_float),&cosangle); ????//注意這里第三個(gè)參數(shù)已經(jīng)改成2，表示二維數(shù)據(jù)。 ????clEnqueueNDRangeKernel(cmdQueue,kernel, ???????????????????????????2,NULL, ???????????????????????????globalWorkSize, ???????????????????????????NULL,0,NULL,NULL); ????//step 8:取回計(jì)算結(jié)果 ????clEnqueueReadBuffer(cmdQueue,bufferB,CL_TRUE,0, ????????????????????????datasize,buf_B,0,NULL,NULL); ????SaveImg(); ????//釋放所有調(diào)用和內(nèi)存 ????clReleaseKernel(kernel); ????clReleaseProgram(program); ????clReleaseCommandQueue(cmdQueue); ????clReleaseMemObject(bufferA); ????clReleaseMemObject(bufferB); ????clReleaseContext(context); ????delete buf_code; ????return 0; }

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源圖

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旋轉(zhuǎn)后圖

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