从文件中读取原始压缩缓冲区.jpg使用 jpeglib

Read raw compressed buffer from file.jpg using jpeglib

本文关键字：缓冲区 jpg 使用 jpeglib 压缩 原始 文件 读取      更新时间：2023-10-16

我希望编写一个代码来打开file.jpg并将数据加载到缓冲区中，而无需实际解压缩数据。我需要按原样发送数据。

我找到了一个读取图像并解压缩它的代码。我不知道如何修改代码以仅获取未解压缩的原始字节版本。

struct jpeg_decompress_struct cinfo;
struct my_error_mgr jerr;
FILE * infile;        /* source file */
JSAMPARRAY buffer;        /* Output row buffer */
int row_stride;       /* physical row width in output buffer */
if ((infile = fopen(filename, "rb")) == NULL) {
fprintf(stderr, "can't open %sn", filename);
return 0;
}
/* Now we can initialize the JPEG decompression object. */
jpeg_create_decompress(&cinfo);
/* Step 2: specify data source (eg, a file) */
jpeg_stdio_src(&cinfo, infile);
(void) jpeg_read_header(&cinfo, TRUE);
// Here I want to only get raw bytes
(void) jpeg_start_decompress(&cinfo);
row_stride = cinfo.output_width * cinfo.output_components;
/* Make a one-row-high sample array that will go away when done with image */
buffer = (*cinfo.mem->alloc_sarray)
((j_common_ptr) &cinfo, JPOOL_IMAGE, row_stride, 1);
while (cinfo.output_scanline < cinfo.output_height) {
(void) jpeg_read_scanlines(&cinfo, buffer, 1);
/* Assume put_scanline_someplace wants a pointer and sample count. */
// put_scanline_someplace(buffer[0], row_stride);
}
/* Step 7: Finish decompression */
(void) jpeg_finish_decompress(&cinfo);      
jpeg_destroy_decompress(&cinfo);
fclose(infile);

在问题帖子下方交换评论后，事实证明，如果我们不关心解压缩，简单的字节读取就足够了。以下是解决问题的代码：

char* data = (char*)malloc(max_w*max_h*3 +100); 
if (data == NULL) {
printf("Input data must not be NULL.n");
return 0;
}
FILE *fp = fopen(filename, "rb"); /* b - binary mode */
if (fp == NULL) {
printf("Error opening file %sn", filename);
return 0;
}
struct stat filestatus;
stat(filename, &filestatus);
size_t data_size = filestatus.st_size;
size_t len = fread(data, 1, data_size , fp);
if (len != data_size) {
printf("Error reading file %sn", filename);
return 0;
}
fclose(fp);
return len;
// free(data) when you are done.
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