DATE： 2019-1-12
1、前言
在看JPEG标准实现时，除了工业级开源实现libjpeg，还发现了这个turbo-jpeg（BSD开源协议），这里只是简单运行和了解了一下，后续可以好好研究学习一下。
turbo-jpeg进行了很多SIMD优化（MMX，SSE2，NEON，AltiVec），据说是libjpeg性能的2~6倍，性能应该不错。
2、turbo-jpeg简介
libjpeg-turbo is a JPEG image codec that uses SIMD instructions (MMX, SSE2, NEON, AltiVec) to accelerate baseline JPEG compression and decompression on x86, x86-64, ARM, and PowerPC systems. On such systems, libjpeg-turbo is generally 2-6x as fast as libjpeg, all else being equal. On other types of systems, libjpeg-turbo can still outperform libjpeg by a significant amount, by virtue of its highly-optimized Huffman coding routines. In many cases, the performance of libjpeg-turbo rivals that of proprietary high-speed JPEG codecs.
libjpeg-turbo implements both the traditional libjpeg API as well as the less powerful but more straightforward TurboJPEG API. libjpeg-turbo also features colorspace extensions that allow it to compress from/decompress to 32-bit and big-endian pixel buffers (RGBX, XBGR, etc.), as well as a full-featured Java interface.
Features
- 2-6x as fast as libjpeg on x86, x86-64, and ARM platforms
- 32-bit and 64-bit binaries provided for popular Linux distributions, Windows, OS X, and iOS
- Can be used in GPL and proprietary applications
- Provides the industry-standard libjpeg API/ABI (can emulate libjpeg v6b, v7, or v8, although libjpeg-turbo does not support the non-standard SmartScale format introduced in libjpeg v8)
- Provides the TurboJPEG API used by VirtualGL and TurboVNC
- Similar performance to commercial/closed source accelerated JPEG codecs
- Full-featured Java wrapper
代码下载：
https://github.com/libjpeg-turbo/libjpeg-turbo
https://sourceforge.net/projects/libjpeg-turbo/
参考：
https://blog.csdn.net/subfate/article/details/46794455
3、turbo-jpeg编译过程
cd {build_directory}
cmake -G"Unix Makefiles" [additional CMake flags] {source_directory}
make
在编译目录中会生成库文件libjpeg.so, libjpeg.a,libturbojpeg.a,libturbojpeg.a；
以及可执行文件djpeg和cjpeg，cjpeg-static和djpeg-static。
更多参考：https://github.com/libjpeg-turbo/libjpeg-turbo/blob/master/BUILDING.md
4、代码示例
/*
* The main program.
*/
int
main(int argc, char **argv)
{
struct jpeg_compress_struct cinfo;
struct jpeg_error_mgr jerr;
#ifdef PROGRESS_REPORT
struct cdjpeg_progress_mgr progress;
#endif
int file_index;
cjpeg_source_ptr src_mgr;
FILE *input_file;
FILE *icc_file;
JOCTET *icc_profile = NULL;
long icc_len = 0;
FILE *output_file = NULL;
unsigned char *outbuffer = NULL;
unsigned long outsize = 0;
JDIMENSION num_scanlines;
/* On Mac, fetch a command line. */
#ifdef USE_CCOMMAND
argc = ccommand(&argv);
#endif
progname = argv[0];
if (progname == NULL || progname[0] == 0)
progname = "cjpeg"; /* in case C library doesn't provide it */
/* Initialize the JPEG compression object with default error handling. */
cinfo.err = jpeg_std_error(&jerr);
jpeg_create_compress(&cinfo);
/* Add some application-specific error messages (from cderror.h) */
jerr.addon_message_table = cdjpeg_message_table;
jerr.first_addon_message = JMSG_FIRSTADDONCODE;
jerr.last_addon_message = JMSG_LASTADDONCODE;
/* Initialize JPEG parameters.
* Much of this may be overridden later.
* In particular, we don't yet know the input file's color space,
* but we need to provide some value for jpeg_set_defaults() to work.
*/
cinfo.in_color_space = JCS_RGB; /* arbitrary guess */
jpeg_set_defaults(&cinfo);
/* Scan command line to find file names.
* It is convenient to use just one switch-parsing routine, but the switch
* values read here are ignored; we will rescan the switches after opening
* the input file.
*/
file_index = parse_switches(&cinfo, argc, argv, 0, FALSE);
#ifdef TWO_FILE_COMMANDLINE
if (!memdst) {
/* Must have either -outfile switch or explicit output file name */
if (outfilename == NULL) {
if (file_index != argc - 2) {
fprintf(stderr, "%s: must name one input and one output file
",
progname);
usage();
}
outfilename = argv[file_index + 1];
} else {
if (file_index != argc - 1) {
fprintf(stderr, "%s: must name one input and one output file
",
progname);
usage();
}
}
}
#else
/* Unix style: expect zero or one file name */
if (file_index < argc - 1) {
fprintf(stderr, "%s: only one input file
", progname);
usage();
}
#endif /* TWO_FILE_COMMANDLINE */
/* Open the input file. */
if (file_index < argc) {
if ((input_file = fopen(argv[file_index], READ_BINARY)) == NULL) {
fprintf(stderr, "%s: can't open %s
", progname, argv[file_index]);
exit(EXIT_FAILURE);
}
} else {
/* default input file is stdin */
input_file = read_stdin();
}
/* Open the output file. */
if (outfilename != NULL) {
if ((output_file = fopen(outfilename, WRITE_BINARY)) == NULL) {
fprintf(stderr, "%s: can't open %s
", progname, outfilename);
exit(EXIT_FAILURE);
}
} else if (!memdst) {
/* default output file is stdout */
output_file = write_stdout();
}
if (icc_filename != NULL) {
if ((icc_file = fopen(icc_filename, READ_BINARY)) == NULL) {
fprintf(stderr, "%s: can't open %s
", progname, icc_filename);
exit(EXIT_FAILURE);
}
if (fseek(icc_file, 0, SEEK_END) < 0 ||
(icc_len = ftell(icc_file)) < 1 ||
fseek(icc_file, 0, SEEK_SET) < 0) {
fprintf(stderr, "%s: can't determine size of %s
", progname,
icc_filename);
exit(EXIT_FAILURE);
}
if ((icc_profile = (JOCTET *)malloc(icc_len)) == NULL) {
fprintf(stderr, "%s: can't allocate memory for ICC profile
", progname);
fclose(icc_file);
exit(EXIT_FAILURE);
}
if (fread(icc_profile, icc_len, 1, icc_file) < 1) {
fprintf(stderr, "%s: can't read ICC profile from %s
", progname,
icc_filename);
free(icc_profile);
fclose(icc_file);
exit(EXIT_FAILURE);
}
fclose(icc_file);
}
#ifdef PROGRESS_REPORT
start_progress_monitor((j_common_ptr)&cinfo, &progress);
#endif
/* Figure out the input file format, and set up to read it. */
src_mgr = select_file_type(&cinfo, input_file);
src_mgr->input_file = input_file;
/* Read the input file header to obtain file size & colorspace. */
(*src_mgr->start_input) (&cinfo, src_mgr);
/* Now that we know input colorspace, fix colorspace-dependent defaults */
jpeg_default_colorspace(&cinfo);
/* Adjust default compression parameters by re-parsing the options */
file_index = parse_switches(&cinfo, argc, argv, 0, TRUE);
/* Specify data destination for compression */
#if JPEG_LIB_VERSION >= 80 || defined(MEM_SRCDST_SUPPORTED)
if (memdst)
jpeg_mem_dest(&cinfo, &outbuffer, &outsize);
else
#endif
jpeg_stdio_dest(&cinfo, output_file);
/* Start compressor */
jpeg_start_compress(&cinfo, TRUE);
if (icc_profile != NULL)
jpeg_write_icc_profile(&cinfo, icc_profile, (unsigned int)icc_len);
/* Process data */
while (cinfo.next_scanline < cinfo.image_height) {
num_scanlines = (*src_mgr->get_pixel_rows) (&cinfo, src_mgr);
(void)jpeg_write_scanlines(&cinfo, src_mgr->buffer, num_scanlines);
}
/* Finish compression and release memory */
(*src_mgr->finish_input) (&cinfo, src_mgr);
jpeg_finish_compress(&cinfo);
jpeg_destroy_compress(&cinfo);
/* Close files, if we opened them */
if (input_file != stdin)
fclose(input_file);
if (output_file != stdout && output_file != NULL)
fclose(output_file);
#ifdef PROGRESS_REPORT
end_progress_monitor((j_common_ptr)&cinfo);
#endif
if (memdst) {
fprintf(stderr, "Compressed size: %lu bytes
", outsize);
if (outbuffer != NULL)
free(outbuffer);
}
if (icc_profile != NULL)
free(icc_profile);
/* All done. */
exit(jerr.num_warnings ? EXIT_WARNING : EXIT_SUCCESS);
return 0; /* suppress no-return-value warnings */
}