c - 当 jpeg_mem_dest 分配空闲缓冲区时发生错误访问

Question

我正在使用 jpeglib 压缩 jpeg。正如文档所说，我需要自己释放缓冲区“mem”。但是当 jpeg_finish_compress 或 jpeg_destroy_compress 之后的 free(mem) 时它崩溃了，说 access violate。

还有一个人和我有同样的问题。

我有什么错误吗？谢谢!

/* Step 1: allocate and initialize JPEG compression object */
jpeg_compress_struct cinfo;
jpeg_error_mgr jerr;
cinfo.err = jpeg_std_error(&jerr);
jpeg_create_compress(&cinfo);
cinfo.input_components = 3;
cinfo.in_color_space = JCS_RGB;

cinfo.image_width = width;
cinfo.image_height = height;
unsigned char* mem = NULL;
unsigned long memSize = 0;
jpeg_mem_dest(&cinfo, &mem, &memSize);

jpeg_set_defaults(&cinfo);

jpeg_set_quality(&cinfo, quality, TRUE);

/* Step 4: Start compressor */
jpeg_start_compress(&cinfo, true);

/* pointer to JSAMPLE row[s] */
JSAMPROW row_pointer[1];

/* Step 5: while (scan lines remain to be written) */
/*           jpeg_write_scanlines(...); */
while (cinfo.next_scanline < cinfo.image_height) {
    row_pointer[0] = &newImgData[cinfo.next_scanline * width * 3];
    jpeg_write_scanlines(&cinfo, row_pointer, 1);
}

/* Step 6: Finish compression */
jpeg_finish_compress(&cinfo);
//free(newImgData);
/* Step 7: release JPEG compression object */
/* This is an important step since it will release a good deal of memory. */
jpeg_destroy_compress(&cinfo);

free(newImgData);

Answer 1

代码没有意义，动态分配的缓冲区位于名为 mem 的变量中，但您正试图释放名为 newImgData 的变量。