c++ - 从 QByteArray 使用 libjpeg 加载 jpeg 图像纹理

Question

您好，我有一个从 QNetworkReply 获得的 jpeg 图像的 QByteArray。我到处都看到从文件中读取 jpeg 图像并像这样解压缩，

FILE * infile;
......
if ((infile = fopen(filename, "rb")) == NULL) 
{
     fprintf(stderr, "can't open %s\n", filename);
     exit(1);
}
jpeg_stdio_src(&cinfo, infile);
jpeg_read_header(&cinfo, 0);
jpeg_start_decompress(&cinfo);

然后

while (scan lines remain to be read)
      jpeg_read_scanlines(...);

但是我如何从 QByteArray 而不是文件/stdio 流中读取它呢？

Answer 1

使用

void jpeg_mem_src(j_decompress_ptr cinfo, unsigned char * inbuffer,
              unsigned long insize);

代替 jpeg_stdio_src

 QByteArray qarr;

 jpeg_decompress_struct cinfo;
 jpeg_mem_src(&cinfo, qarr.data(), qarr.size());
 jpeg_read_header(&cinfo, TRUE);
 jpeg_start_decompress(&cinfo);

 /// etc..