libjpeg样例

#include <stdio.h>
#include <stdlib.h>
#include <memory.h>
#include <math.h>
#include "bmp.h"
#include "jpeg-8b/jpeglib.h"

#pragma comment( lib , "jpeg-8b/libjpeg.lib" )

char * bmpFileName = "input.bmp";
char * jpgFileName = "output.jpg";

BITMAPFILEHEADER fileHeader;
BITMAPINFOHEADER infoHeader;

long width = 0;
long height = 0;
//=============================================================

unsigned char * RGB_Ptr = NULL;
//=============================================================
long getSize(int hByte,int lByte){
    long result = (hByte/16)*(16*16*16);
    result += (hByte%16)*(16*16);
    result += (lByte/16)*(16);
    result += (lByte%16)*(1);
    return result;
}
//=====================================================================


int main(){
    FILE * f1 = NULL;
    FILE * f2 = NULL;
    struct jpeg_compress_struct jcs;
    struct jpeg_error_mgr jem;
    jcs.err = jpeg_std_error(&jem);
    jpeg_create_compress(&jcs);
    //result.jpg
    
    {
        f1=fopen(jpgFileName,"wb");
        jpeg_stdio_dest(&jcs, f1);
    }
    
    {//读取bmp信息
        long biWidth = 0;
        long biHeight = 0;
        f2 = fopen(bmpFileName,"rb");
        if(f2 == NULL){
            printf("找不到文件\n");
            return 0;
        }
        memset(&fileHeader, 0, sizeof(fileHeader));
        fread(&fileHeader, sizeof(fileHeader), 1, f2);
        memset(&infoHeader, 0, sizeof(infoHeader));
        fread(&infoHeader, sizeof(infoHeader), 1, f2);
        width = getSize(infoHeader.biWidth[1],infoHeader.biWidth[0]);
        height = getSize(infoHeader.biHeight[1],infoHeader.biHeight[0]);
        printf(" 图片宽度%ld ; 图片长度%ld ;\n",width,height);

        fseek(f2, 54, SEEK_SET); //放置指针到像素第一个
        //总字节数 = 宽 x 高 x 3 ;
        RGB_Ptr = malloc(width*height*3+1);
        fread(RGB_Ptr,width*height*3,1,f2);
        fclose(f2);
    }
    
    {
        jcs.image_width = width; //
        jcs.image_height = height; //
        jcs.input_components = 3; //
        jcs.in_color_space = JCS_RGB; //JCS_GRAYSCALE
        jpeg_set_defaults(&jcs);
        jpeg_set_quality (&jcs, 80, 1);
    }
    
    jpeg_start_compress(&jcs, 1);
    {
        int i=0;
        long rgb_index = height * width * 3 - 1;

        //===========================================================
        //逐行写入RGB_Ptr

        JSAMPROW row_pointer[1];
        for(i=0;i<height;i++){
            int j=0;
            unsigned char * lineData = NULL;
            lineData = malloc(width*3);
            for(j=0;j<width;j++){
                lineData[(width-j-1)*3+0] = RGB_Ptr[rgb_index];
                rgb_index --;
                lineData[(width-j-1)*3+1] = RGB_Ptr[rgb_index];
                rgb_index --;
                lineData[(width-j-1)*3+2] = RGB_Ptr[rgb_index];
                rgb_index --;
            }
            row_pointer[0] = lineData;
            jpeg_write_scanlines(&jcs, row_pointer, 1);
            
        }
        

        /*
        JSAMPROW * row_pointer;
        rgb_index = 0;
        //一次写入
        row_pointer = malloc(height*width*3);
        for(i=0;i<height;i++){
            int j=0;
            unsigned char * lineData = NULL;
            lineData = malloc(width*3);
            for(j=0;j<width;j++){
                lineData[j*3+2] = RGB_Ptr[rgb_index];
                rgb_index ++;
                lineData[j*3+1] = RGB_Ptr[rgb_index];
                rgb_index ++;
                lineData[j*3+0] = RGB_Ptr[rgb_index];
                rgb_index ++;
            }
            row_pointer[height-i-1] = lineData;
        }
        jpeg_write_scanlines(&jcs, row_pointer, height);
        */
        
    }
    jpeg_finish_compress(&jcs);
    jpeg_destroy_compress(&jcs);
    
    
    fclose(f1);
    return 0;
}