Tga常见的格式有非压缩RGB和压缩RGB两种格式，其他格式的我们在这里不做讲述。文件的第三个Byte位作为标记：2为非压缩RGB格式，10为压缩RGB格式。在此次实验中，分析未压缩的tga图片。
未压缩格式：
名称偏移长度说明图像信息字段长度01本字段为1字节无符号整型，指出图像信息字段的长度，其取值范围为0~255，当它为0时，表示没有图像的信息字段颜色表类型110表示没有颜色表，1表示颜色表存在图像类型码21该字段总为2，表示无压缩图像颜色表首址32颜色表首的入口索引，整型（低位-高位）颜色表的长度52颜色表的表项总数，整型（低位-高位）颜色表项位数71位数（bit），16代表16位TGA,24位代表24位TGA，32代表32位TGA图像X坐标起始位置82图像左下角X坐标的整型值图像Y坐标其实位置102图像左下角Y坐标的整型值图像宽度122以像素为单位，图像宽度的整型图像高度142以像素为单位，图像高度的整型图像每像素存储占用位数162它的值为16，24或32等等，决定了该图像时TGA16，TGA24,TGA32等等图像描述字节171bits 3-0 - 每像素对应的属性位的位数；对于TGA 16，该值为 0 或 1，对于 TGA24，该值为 0，对于 TGA 32，该值为 8。 bit 4 - 保留，必须为 0。bit 5 - 屏幕起始位置标志，0 = 原点在左下角，1 = 原点在左上角对于 truevision 图像必须为 0。bits 7-6 - 交叉数据存储标志：00 = 无交叉；01 = 两wndxh/偶交叉；10 = 四路交叉；11 = 保留图像信息字段18可变包含一个自由格式的，长度是图像由“图像信息字段”指定。它常常被忽略（即偏移 0 处值为 0 ），注意其最大可以含有 255 个字符。如果需要存储更多信息，可以放在图像数据之后颜色表数据可变可变如果颜色类型为0，则该域不存在，否则越过该域直接读取图像颜色表规格中描述了每项的字节数，为2，3，4之一图像数据可变可变RGB颜色数据，存放顺序为BGR，数据从图像左下角开始存储参考：文件格式分析
二：代码部分rgb2yuv.cpp
#include <stdio.h>#include <iostream>#include <malloc.h>#include"TgaHeader.h"int rgb2yuv(void* rgb_s, void* y_s, void* u_s, void* v_s, int W, int H){unsigned char *r = NULL, *g = NULL, *b = NULL, *rgb = NULL;unsigned char *y, *u, *v, *U, *V;rgb = (unsigned char *)rgb_s;y = (unsigned char *)y_s;u = (unsigned char *)u_s;v = (unsigned char *)v_s;r = (unsigned char *)malloc(sizeof(char)*(W*H));g = (unsigned char *)malloc(sizeof(char)*(W*H));b = (unsigned char *)malloc(sizeof(char)*(W*H));U = (unsigned char *)malloc(sizeof(char)*(W*H));V = (unsigned char *)malloc(sizeof(char)*(W*H));int j=0;for (int i = 0; i < W*H; i++){b[i] = rgb[j];g[i] = rgb[j+1];r[i] = rgb[j+2];j += 3;}for (int i = 0; i < H*W; i++){y[i] = r[i]*0.2990 + g[i]*0.5870 + b[i]*0.1140;U[i] = r[i]*(-0.1684) - g[i]*0.3316 + b[i]*0.5 + 128;V[i] = r[i]*0.5 - g[i]*0.4187 - b[i]*0.0813 + 128;}int k = 0;for (int i = 0; i < H; i = i + 2){for (j = 0; j < W; j = j + 2){u[k] = (U[W*i + j] + U[W*i + j + 1] + U[(i + 1)*W + j] + U[(i + 1)*W + j + 1]) / 4;v[k] = (V[W*i + j] + V[W*i + j + 1] + V[(i + 1)*W + j] + V[(i + 1)*W + j + 1]) / 4;k++;}}return 0;}main.cpp
#include <stdio.h>#include <iostream>#include <malloc.h>#include"TgaHeader.h"using namespace std;struct TGA_HEADER{unsigned short IDLength;unsigned short ImageType;unsigned short ColorMapLen;unsigned char ColorMapBits;unsigned int Width;unsigned int Height;unsigned char bitsPerPixel;}TGAHEADER;int main(int argc, char **argv){FILE *TgaFile = NULL;FILE *YuvFile = NULL;char *TgaFileName = NULL;char *YuvFileName = NULL;TgaFileName = argv[1];YuvFileName = argv[2];int Height, Width;int offset = 0;if (fopen_s(&TgaFile, TgaFileName, "rb") == 0)printf("The tgafile was opened: %s n", TgaFileName);else printf("The tgafile cannot open: %s n", TgaFileName);fopen_s(&YuvFile, YuvFileName, "wb");unsigned char typeHeader[18] = { 0 };fread(typeHeader, 1, 18, TgaFile);TGAHEADER.IDLength = typeHeader[0];TGAHEADER.ImageType = typeHeader[2];TGAHEADER.ColorMapLen = (typeHeader[6] << 8) + typeHeader[5];TGAHEADER.ColorMapBits = typeHeader[7];TGAHEADER.Width = (typeHeader[13] << 8) + typeHeader[12];TGAHEADER.Height = (typeHeader[15] << 8) + typeHeader[14];TGAHEADER.bitsPerPixel = (typeHeader[17] << 8) + typeHeader[16];unsigned short pixel = TGAHEADER.bitsPerPixel / 8;unsigned short ColorPixel = TGAHEADER.ColorMapBits / 8;Width = TGAHEADER.Width;Height = TGAHEADER.Height;printf("该tga图片的大小为: %d * %d n", TGAHEADER.Width, TGAHEADER.Height);int i, j;unsigned char *tgaBuffer = NULL;unsigned char *rgbBuffer = NULL;unsigned char *yBuffer = NULL;unsigned char *uBuffer = NULL;unsigned char *vBuffer = NULL;unsigned char *colorBuffer = NULL;unsigned char *colormapBuffer = NULL;yBuffer = (unsigned char *)malloc(Width*Height);uBuffer = (unsigned char *)malloc(Width*Height / 4);vBuffer = (unsigned char *)malloc(Width*Height / 4); tgaBuffer = (unsigned char *)malloc(Width*Height * 3);rgbBuffer = (unsigned char *)malloc(Width*Height * 3);offset = TGAHEADER.IDLength + 18;fseek(TgaFile, offset, SEEK_SET);switch (pixel){case 3:fread(tgaBuffer, 1, Width*Height*pixel, TgaFile);break;case 4:unsigned char *tgaB = NULL;fread(tgaB, 1, Width*Height*pixel, TgaFile);int a = 0, b = 0;for (i = 0; i < Height; i++){for (j = 0; j < Width; j++){tgaBuffer[a] = tgaB[b];tgaBuffer[a + 1] = tgaB[b + 1];tgaBuffer[a + 2] = tgaB[b + 2];a += 3;b += 4;}}free(tgaB);}for(i=0;i<Height;i++)for (j = 0; j < Width * 3; j++){rgbBuffer[Width * 3 * i + j] = tgaBuffer[Width * 3 * (Height - i - 1) + j];}if((rgb2yuv(rgbBuffer,yBuffer,uBuffer,vBuffer,Width,Height)==0))printf("yuvFile has finishedn");else{printf("errorn");exit(1);}fwrite(yBuffer, 1, Width*Height, YuvFile);fwrite(uBuffer, 1, Width*Height/4, YuvFile);fwrite(vBuffer, 1, Width*Height/4, YuvFile);free(yBuffer);free(uBuffer);free(vBuffer);free(tgaBuffer);free(rgbBuffer); fclose(TgaFile);fclose(YuvFile);return 0;}TgaHeader.h
#pragma onceint rgb2yuv(void* rgb_s, void* y_s, void* u_s, void* v_s, int W, int H); 三：实验结果原图tga：
转换结果yuv：