用libjpeg把jpg转换成winapi的bmp（BITMAP）

#include <stdio.h> // jpeglib需要FILE和size_t的定义
#include <windows.h>
#include "debug.h"
#include "jpeglib.h"
#pragma comment(lib, "libjpeg.lib")

extern HBITMAP jpg2bmp(unsigned char *jpg_buffer, unsigned jpg_size)
{
    int rc;
    struct jpeg_decompress_struct cinfo;
    struct jpeg_error_mgr jerr;
    BITMAPINFO bi; // = {};
    LPBYTE lpBuf, pb = NULL;
    HBITMAP hbm;    
    JSAMPARRAY buffer; // {};
    INT row = 0;
    
    DEBUG_PUTS("读取jpg");

    cinfo.err = jpeg_std_error(&jerr);
    jpeg_create_decompress(&cinfo);

    jpeg_mem_src(&cinfo, jpg_buffer, jpg_size);

    rc = jpeg_read_header(&cinfo, TRUE); // read jpeg file header

    if (rc != 1) {
        // File does not seem to be a normal JPEG
        return NULL;
    }
    
    jpeg_start_decompress(&cinfo);  // decompress the file

    row = ((cinfo.output_width * 3 + 3) & ~3);
    buffer = (*cinfo.mem->alloc_sarray)((j_common_ptr)&cinfo, JPOOL_IMAGE,
        row, 1);

    ZeroMemory(&bi.bmiHeader, sizeof(BITMAPINFOHEADER));
    bi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
    bi.bmiHeader.biWidth = cinfo.output_width;
    bi.bmiHeader.biHeight = cinfo.output_height;
    bi.bmiHeader.biPlanes = 1;
    bi.bmiHeader.biBitCount = 24;
    bi.bmiHeader.biCompression = BI_RGB;
    bi.bmiHeader.biSizeImage = row * cinfo.output_height;

    hbm = CreateDIBSection(NULL, &bi, DIB_RGB_COLORS, (void**)&lpBuf, NULL, 0);
    
    if (hbm == NULL)
    {
        DEBUG_PUTS("hbm NULL");
        jpeg_destroy_decompress(&cinfo);
        return NULL;
    }
    
    DEBUG_PUTS("hbm正常");

    pb = lpBuf + row * cinfo.output_height;
    DEBUG_PRINTF("行 %d 输出高度 %d
", row, cinfo.output_height);
    while (cinfo.output_scanline < cinfo.output_height)
    {
        pb -= row;
        jpeg_read_scanlines(&cinfo, buffer, 1);

        if (cinfo.out_color_components == 1)
        {
            UINT i;
            LPBYTE p = (LPBYTE)buffer[0];
            
            for (i = 0; i < cinfo.output_width; i++)
                pb[3 * i + 0] = pb[3 * i + 1] = pb[3 * i + 2] = p[i];
        }
        else if (cinfo.out_color_components == 3)
        {
            // There was talk on Internet about one being RGB and another BGR. 
            // If colors appear swapped, then swap the bytes, and update this comment.
            // CopyMemory(pb, buffer[0], row);

            // Updated color correction
            UINT i;
            LPBYTE p = (LPBYTE)buffer[0];
            
            for (i = 0; i < row; i += 3)
            {
                pb[i + 0] = p[i + 2]; // Blue
                pb[i + 1] = p[i + 1]; // Green  
                pb[i + 2] = p[i + 0]; // Red
            }
        }
        else
        {
            DEBUG_PUTS("【异常】cinfo.out_color_components无效");
            jpeg_destroy_decompress(&cinfo);
            DeleteObject(hbm);
            return NULL;
        }
    }

    DEBUG_PUTS("即将调用SetDIBits");

    SetDIBits(NULL, hbm, 0, cinfo.output_height, lpBuf, &bi, DIB_RGB_COLORS);

    jpeg_finish_decompress(&cinfo);
    jpeg_destroy_decompress(&cinfo);

    return hbm;
}