/*
* example.c
*
* This file was part of the Independent JPEG Group's software.
* Copyright (C) 1992-1996, Thomas G. Lane.
* libjpeg-turbo Modifications:
* Copyright (C) 2017, 2019, 2022, D. R. Commander.
* For conditions of distribution and use, see the accompanying README.ijg
* file.
*
* This file illustrates how to use the IJG code as a subroutine library
* to read or write JPEG image files with 8-bit or 12-bit data precision. You
* should look at this code in conjunction with the documentation file
* libjpeg.txt.
*
* We present these routines in the same coding style used in the JPEG code
* (ANSI function definitions, etc); but you are of course free to code your
* routines in a different style if you prefer.
*/
/* First-time users of libjpeg-turbo might be better served by looking at
* tjexample.c, which uses the more straightforward TurboJPEG API. Note that
* this example, like cjpeg and djpeg, interleaves disk I/O with JPEG
* compression/decompression, so it is not suitable for benchmarking purposes.
*/
#ifdef _MSC_VER
#define _CRT_SECURE_NO_DEPRECATE
#endif
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#ifdef _WIN32
#define strcasecmp stricmp
#define strncasecmp strnicmp
#endif
/*
* Include file for users of JPEG library.
* You will need to have included system headers that define at least
* the typedefs FILE and size_t before you can include jpeglib.h.
* (stdio.h is sufficient on ANSI-conforming systems.)
* You may also wish to include "jerror.h".
*/
#include "jpeglib.h"
#include "jerror.h"
/*
* <setjmp.h> is used for the optional error recovery mechanism shown in
* the second part of the example.
*/
#include <setjmp.h>
/******************** JPEG COMPRESSION SAMPLE INTERFACE *******************/
/* This half of the example shows how to feed data into the JPEG compressor.
* We present a minimal version that does not worry about refinements such
* as error recovery (the JPEG code will just exit() if it gets an error).
*/
/*
* IMAGE DATA FORMATS:
*
* The standard input image format is a rectangular array of pixels, with
* each pixel having the same number of "component" values (color channels).
* Each pixel row is an array of JSAMPLEs (which typically are unsigned chars)
* or J12SAMPLEs (which typically are shorts). If you are working with color
* data, then the color values for each pixel must be adjacent in the row; for
* example, R,G,B,R,G,B,R,G,B,... for 24-bit RGB color.
*
* For this example, we'll assume that this data structure matches the way
* our application has stored the image in memory, so we can just pass a
* pointer to our image buffer. In particular, let's say that the image is
* RGB color and is described by:
*/
#define WIDTH 640 /* Number of columns in image */
#define HEIGHT 480 /* Number of rows in image */
/*
* Sample routine for JPEG compression. We assume that the target file name,
* a compression quality factor, and a data precision are passed in.
*/
METHODDEF(void)
write_JPEG_file(char *filename, int quality, int data_precision)
{
/* This struct contains the JPEG compression parameters and pointers to
* working space (which is allocated as needed by the JPEG library).
* It is possible to have several such structures, representing multiple
* compression/decompression processes, in existence at once. We refer
* to any one struct (and its associated working data) as a "JPEG object".
*/
struct jpeg_compress_struct cinfo;
/* This struct represents a JPEG error handler. It is declared separately
* because applications often want to supply a specialized error handler
* (see the second half of this file for an example). But here we just
* take the easy way out and use the standard error handler, which will
* print a message on stderr and call exit() if compression fails.
* Note that this struct must live as long as the main JPEG parameter
* struct, to avoid dangling-pointer problems.
*/
struct jpeg_error_mgr jerr;
/* More stuff */
FILE *outfile; /* target file */
JSAMPARRAY image_buffer = NULL;
/* Points to large array of R,G,B-order data */
JSAMPROW row_pointer[1]; /* pointer to JSAMPLE row[s] */
J12SAMPARRAY image_buffer12 = NULL;
/* Points to large array of R,G,B-order 12-bit
data */
J12SAMPROW row_pointer12[1]; /* pointer to J12SAMPLE row[s] */
int row_stride; /* physical row width in image buffer */
int row, col;
/* Step 1: allocate and initialize JPEG compression object */
/* We have to set up the error handler first, in case the initialization
* step fails. (Unlikely, but it could happen if you are out of memory.)
* This routine fills in the contents of struct jerr, and returns jerr's
* address which we place into the link field in cinfo.
*/
cinfo.err = jpeg_std_error(&jerr);
/* Now we can initialize the JPEG compression object. */
jpeg_create_compress(&cinfo);
/* Step 2: specify data destination (eg, a file) */
/* Note: steps 2 and 3 can be done in either order. */
/* Here we use the library-supplied code to send compressed data to a
* stdio stream. You can also write your own code to do something else.
* VERY IMPORTANT: use "b" option to fopen() if you are on a machine that
* requires it in order to write binary files.
*/
if ((outfile = fopen(filename, "wb")) == NULL)
ERREXIT(&cinfo, JERR_FILE_WRITE);
jpeg_stdio_dest(&cinfo, outfile);
/* Step 3: set parameters for compression */
/* First we supply a description of the input image.
* Four fields of the cinfo struct must be filled in:
*/
cinfo.image_width = WIDTH; /* image width and height, in pixels */
cinfo.image_height = HEIGHT;
cinfo.input_components = 3; /* # of color components per pixel */
cinfo.in_color_space = JCS_RGB; /* colorspace of input image */
cinfo.data_precision = data_precision; /* data precision of input image */
/* Now use the library's routine to set default compression parameters.
* (You must set at least cinfo.in_color_space before calling this,
* since the defaults depend on the source color space.)
*/
jpeg_set_defaults(&cinfo);
/* Now you can set any non-default parameters you wish to.
* Here we just illustrate the use of quality (quantization table) scaling:
*/
jpeg_set_quality(&cinfo, quality, TRUE /* limit to baseline-JPEG values */);
/* Use 4:4:4 subsampling (default is 4:2:0) */
cinfo.comp_info[0].h_samp_factor = cinfo.comp_info[0].v_samp_factor = 1;
/* Step 4: Start compressor */
/* TRUE ensures that we will write a complete interchange-JPEG file.
* Pass TRUE unless you are very sure of what you're doing.
*/
jpeg_start_compress(&cinfo, TRUE);
/* Step 5: allocate and initialize image buffer */
row_stride = WIDTH * 3; /* J[12]SAMPLEs per row in image_buffer */
/* Make a sample array that will go away when done with image. Note that,
* for the purposes of this example, we could also create a one-row-high
* sample array and initialize it for each successive scanline written in the
* scanline loop below.
*/
if (cinfo.data_precision == 12) {
image_buffer12 = (J12SAMPARRAY)(*cinfo.mem->alloc_sarray)
((j_common_ptr)&cinfo, JPOOL_IMAGE, row_stride, HEIGHT);
/* Initialize image buffer with a repeating pattern */
for (row = 0; row < HEIGHT; row++) {
for (col = 0; col < WIDTH; col++) {
image_buffer12[row][col * 3] =
(col * (MAXJ12SAMPLE + 1) / WIDTH) % (MAXJ12SAMPLE + 1);
image_buffer12[row][col * 3 + 1] =
(row * (MAXJ12SAMPLE + 1) / HEIGHT) % (MAXJ12SAMPLE + 1);
image_buffer12[row][col * 3 + 2] =
(row * (MAXJ12SAMPLE + 1) / HEIGHT +
col * (MAXJ12SAMPLE + 1) / WIDTH) % (MAXJ12SAMPLE + 1);
}
}
} else {
image_buffer = (*cinfo.mem->alloc_sarray)
((j_common_ptr)&cinfo, JPOOL_IMAGE, row_stride, HEIGHT);
for (row = 0; row < HEIGHT; row++) {
for (col = 0; col < WIDTH; col++) {
image_buffer[row][col * 3] =
(col * (MAXJSAMPLE + 1) / WIDTH) % (MAXJSAMPLE + 1);
image_buffer[row][col * 3 + 1] =
(row * (MAXJSAMPLE + 1) / HEIGHT) % (MAXJSAMPLE + 1);
image_buffer[row][col * 3 + 2] =
(row * (MAXJSAMPLE + 1) / HEIGHT + col * (MAXJSAMPLE + 1) / WIDTH) %
(MAXJSAMPLE + 1);
}
}
}
/* Step 6: while (scan lines remain to be written) */
/* jpeg_write_scanlines(...); */
/* Here we use the library's state variable cinfo.next_scanline as the
* loop counter, so that we don't have to keep track ourselves.
* To keep things simple, we pass one scanline per call; you can pass
* more if you wish, though.
*/
if (cinfo.data_precision == 12) {
while (cinfo.next_scanline < cinfo.image_height) {
/* jpeg12_write_scanlines expects an array of pointers to scanlines.
* Here the array is only one element long, but you could pass
* more than one scanline at a time if that's more convenient.
*/
row_pointer12[0] = image_buffer12[cinfo.next_scanline];
(void)jpeg12_write_scanlines(&cinfo, row_pointer12, 1);
}
} else {
while (cinfo.next_scanline < cinfo.image_height) {
/* jpeg_write_scanlines expects an array of pointers to scanlines.
* Here the array is only one element long, but you could pass
* more than one scanline at a time if that's more convenient.
*/
row_pointer[0] = image_buffer[cinfo.next_scanline];
(void)jpeg_write_scanlines(&cinfo, row_pointer, 1);
}
}
/* Step 7: Finish compression */
jpeg_finish_compress(&cinfo);
/* After finish_compress, we can close the output file. */
fclose(outfile);
/* Step 8: release JPEG compression object */
/* This is an important step since it will release a good deal of memory. */
jpeg_destroy_compress(&cinfo);
/* And we're done! */
}
/*
* SOME FINE POINTS:
*
* In the above loop, we ignored the return value of jpeg_write_scanlines,
* which is the number of scanlines actually written. We could get away
* with this because we were only relying on the value of cinfo.next_scanline,
* which will be incremented correctly. If you maintain additional loop
* variables then you should be careful to increment them properly.
* Actually, for output to a stdio stream you needn't worry, because
* then jpeg_write_scanlines will write all the lines passed (or else exit
* with a fatal error). Partial writes can only occur if you use a data
* destination module that can demand suspension of the compressor.
* (If you don't know what that's for, you don't need it.)
*
* If the compressor requires full-image buffers (for entropy-coding
* optimization or a multi-scan JPEG file), it will create temporary
* files for anything that doesn't fit within the maximum-memory setting.
* (Note that temp files are NOT needed if you use the default parameters.)
* On some systems you may need to set up a signal handler to ensure that
* temporary files are deleted if the program is interrupted. See libjpeg.txt.
*
* Scanlines MUST be supplied in top-to-bottom order if you want your JPEG
* files to be compatible with everyone else's. If you cannot readily read
* your data in that order, you'll need an intermediate array to hold the
* image. See rdtarga.c or rdbmp.c for examples of handling bottom-to-top
* source data using the JPEG code's internal virtual-array mechanisms.
*/
/******************** JPEG DECOMPRESSION SAMPLE INTERFACE *******************/
/* This half of the example shows how to read data from the JPEG decompressor.
* It's a bit more refined than the above, in that we show:
* (a) how to modify the JPEG library's standard error-reporting behavior;
* (b) how to allocate workspace using the library's memory manager.
*
* Just to make this example a little different from the first one, we'll
* assume that we do not intend to put the whole image into an in-memory
* buffer, but to send it line-by-line someplace else. We need a one-
* scanline-high JSAMPLE or J12SAMPLE array as a work buffer, and we will let
* the JPEG memory manager allocate it for us. This approach is actually quite
* useful because we don't need to remember to deallocate the buffer
* separately: it will go away automatically when the JPEG object is cleaned
* up.
*/
/*
* ERROR HANDLING:
*
* The JPEG library's standard error handler (jerror.c) is divided into
* several "methods" which you can override individually. This lets you
* adjust the behavior without duplicating a lot of code, which you might
* have to update with each future release.
*
* Our example here shows how to override the "error_exit" method so that
* control is returned to the library's caller when a fatal error occurs,
* rather than calling exit() as the standard error_exit method does.
*
* We use C's setjmp/longjmp facility to return control. This means that the
* routine which calls the JPEG library must first execute a setjmp() call to
* establish the return point. We want the replacement error_exit to do a
* longjmp(). But we need to make the setjmp buffer accessible to the
* error_exit routine. To do this, we make a private extension of the
* standard JPEG error handler object. (If we were using C++, we'd say we
* were making a subclass of the regular error handler.)
*
* Here's the extended error handler struct:
*/
struct my_error_mgr {
struct jpeg_error_mgr pub; /* "public" fields */
jmp_buf setjmp_buffer; /* for return to caller */
};
typedef struct my_error_mgr *my_error_ptr;
/*
* Here's the routine that will replace the standard error_exit method:
*/
METHODDEF(void)
my_error_exit(j_common_ptr cinfo)
{
/* cinfo->err really points to a my_error_mgr struct, so coerce pointer */
my_error_ptr myerr = (my_error_ptr)cinfo->err;
/* Always display the message. */
/* We could postpone this until after returning, if we chose. */
(*cinfo->err->output_message) (cinfo);
/* Return control to the setjmp point */
longjmp(myerr->setjmp_buffer, 1);
}
METHODDEF(int) do_read_JPEG_file(struct jpeg_decompress_struct *cinfo,
char *infilename, char *outfilename);
/*
* Sample routine for JPEG decompression. We assume that the source file name
* is passed in. We want to return 1 on success, 0 on error.
*/
METHODDEF(int)
read_JPEG_file(char *infilename, char *outfilename)
{
/* This struct contains the JPEG decompression parameters and pointers to
* working space (which is allocated as needed by the JPEG library).
*/
struct jpeg_decompress_struct cinfo;
return do_read_JPEG_file(&cinfo, infilename, outfilename);
}
/*
* We call the libjpeg API from within a separate function, because modifying
* the local non-volatile jpeg_decompress_struct instance below the setjmp()
* return point and then accessing the instance after setjmp() returns would
* result in undefined behavior that may potentially overwrite all or part of
* the structure.
*/
METHODDEF(int)
do_read_JPEG_file(struct jpeg_decompress_struct *cinfo, char *infilename,
char *outfilename)
{
/* We use our private extension JPEG error handler.
* Note that this struct must live as long as the main JPEG parameter
* struct, to avoid dangling-pointer problems.
*/
struct my_error_mgr jerr;
/* More stuff */
FILE *infile; /* source file */
FILE *outfile; /* output file */
JSAMPARRAY buffer = NULL; /* Output row buffer */
J12SAMPARRAY buffer12 = NULL; /* 12-bit output row buffer */
int col;
int row_stride; /* physical row width in output buffer */
/* In this example we want to open the input and output files before doing
* anything else, so that the setjmp() error recovery below can assume the
* files are open.
*
* VERY IMPORTANT: use "b" option to fopen() if you are on a machine that
* requires it in order to read/write binary files.
*/
if ((infile = fopen(infilename, "rb")) == NULL) {
fprintf(stderr, "can't open %s\n", infilename);
return 0;
}
if ((outfile = fopen(outfilename, "wb")) == NULL) {
fprintf(stderr, "can't open %s\n", outfilename);
fclose(infile);
return 0;
}
/* Step 1: allocate and initialize JPEG decompression object */
/* We set up the normal JPEG error routines, then override error_exit. */
cinfo->err = jpeg_std_error(&jerr.pub);
jerr.pub.error_exit = my_error_exit;
/* Establish the setjmp return context for my_error_exit to use. */
if (setjmp(jerr.setjmp_buffer)) {
/* If we get here, the JPEG code has signaled an error.
* We need to clean up the JPEG object, close the input file, and return.
*/
jpeg_destroy_decompress(cinfo);
fclose(infile);
fclose(outfile);
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);
/* Step 3: read file parameters with jpeg_read_header() */
(void)jpeg_read_header(cinfo, TRUE);
/* We can ignore the return value from jpeg_read_header since
* (a) suspension is not possible with the stdio data source, and
* (b) we passed TRUE to reject a tables-only JPEG file as an error.
* See libjpeg.txt for more info.
*/
/* emit header for raw PPM format */
fprintf(outfile, "P6\n%d %d\n%d\n", WIDTH, HEIGHT,
cinfo->data_precision == 12 ? MAXJ12SAMPLE : MAXJSAMPLE);
/* Step 4: set parameters for decompression */
/* In this example, we don't need to change any of the defaults set by
* jpeg_read_header(), so we do nothing here.
*/
/* Step 5: Start decompressor */
(void)jpeg_start_decompress(cinfo);
/* We can ignore the return value since suspension is not possible
* with the stdio data source.
*/
/* We may need to do some setup of our own at this point before reading
* the data. After jpeg_start_decompress() we have the correct scaled
* output image dimensions available, as well as the output colormap
* if we asked for color quantization.
* In this example, we need to make an output work buffer of the right size.
*/
/* Samples per row in output buffer */
row_stride = cinfo->output_width * cinfo->output_components;
/* Make a one-row-high sample array that will go away when done with image */
if (cinfo->data_precision == 12)
buffer12 = (J12SAMPARRAY)(*cinfo->mem->alloc_sarray)
((j_common_ptr)cinfo, JPOOL_IMAGE, row_stride, 1);
else
buffer = (*cinfo->mem->alloc_sarray)
((j_common_ptr)cinfo, JPOOL_IMAGE, row_stride, 1);
/* Step 6: while (scan lines remain to be read) */
/* jpeg_read_scanlines(...); */
/* Here we use the library's state variable cinfo->output_scanline as the
* loop counter, so that we don't have to keep track ourselves.
*/
if (cinfo->data_precision == 12) {
while (cinfo->output_scanline < cinfo->output_height) {
/* jpeg12_read_scanlines expects an array of pointers to scanlines.
* Here the array is only one element long, but you could ask for
* more than one scanline at a time if that's more convenient.
*/
(void)jpeg12_read_scanlines(cinfo, buffer12, 1);
/* Swap MSB and LSB in each sample */
for (col = 0; col < row_stride; col++)
buffer12[0][col] = ((buffer12[0][col] & 0xFF) << 8) |
((buffer12[0][col] >> 8) & 0xFF);
fwrite(buffer12[0], 1, row_stride * sizeof(J12SAMPLE), outfile);
}
} else {
while (cinfo->output_scanline < cinfo->output_height) {
/* jpeg_read_scanlines expects an array of pointers to scanlines.
* Here the array is only one element long, but you could ask for
* more than one scanline at a time if that's more convenient.
*/
(void)jpeg_read_scanlines(cinfo, buffer, 1);
fwrite(buffer[0], 1, row_stride, outfile);
}
}
/* Step 7: Finish decompression */
(void)jpeg_finish_decompress(cinfo);
/* We can ignore the return value since suspension is not possible
* with the stdio data source.
*/
/* Step 8: Release JPEG decompression object */
/* This is an important step since it will release a good deal of memory. */
jpeg_destroy_decompress(cinfo);
/* After finish_decompress, we can close the input and output files.
* Here we postpone it until after no more JPEG errors are possible,
* so as to simplify the setjmp error logic above. (Actually, I don't
* think that jpeg_destroy can do an error exit, but why assume anything...)
*/
fclose(infile);
fclose(outfile);
/* At this point you may want to check to see whether any corrupt-data
* warnings occurred (test whether jerr.pub.num_warnings is nonzero).
*/
/* And we're done! */
return 1;
}
/*
* SOME FINE POINTS:
*
* In the above code, we ignored the return value of jpeg_read_scanlines,
* which is the number of scanlines actually read. We could get away with
* this because we asked for only one line at a time and we weren't using
* a suspending data source. See libjpeg.txt for more info.
*
* We cheated a bit by calling alloc_sarray() after jpeg_start_decompress();
* we should have done it beforehand to ensure that the space would be
* counted against the JPEG max_memory setting. In some systems the above
* code would risk an out-of-memory error. However, in general we don't
* know the output image dimensions before jpeg_start_decompress(), unless we
* call jpeg_calc_output_dimensions(). See libjpeg.txt for more about this.
*
* Scanlines are returned in the same order as they appear in the JPEG file,
* which is standardly top-to-bottom. If you must emit data bottom-to-top,
* you can use one of the virtual arrays provided by the JPEG memory manager
* to invert the data. See wrbmp.c for an example.
*
* As with compression, some operating modes may require temporary files.
* On some systems you may need to set up a signal handler to ensure that
* temporary files are deleted if the program is interrupted. See libjpeg.txt.
*/
LOCAL(void)
usage(const char *progname)
{
fprintf(stderr, "usage: %s compress [switches] outputfile[.jpg]\n",
progname);
fprintf(stderr, " %s decompress inputfile[.jpg] outputfile[.ppm]\n",
progname);
fprintf(stderr, "Switches (names may be abbreviated):\n");
fprintf(stderr, " -precision N Create JPEG file with N-bit data precision\n");
fprintf(stderr, " (N is 8 or 12; default is 8)\n");
fprintf(stderr, " -quality N Compression quality (0..100; 5-95 is most useful range,\n");
fprintf(stderr, " default is 75)\n");
exit(EXIT_FAILURE);
}
typedef enum {
COMPRESS,
DECOMPRESS
} EXAMPLE_MODE;
int
main(int argc, char **argv)
{
int argn, quality = 75;
int data_precision = 8;
EXAMPLE_MODE mode = -1;
char *arg, *filename = NULL;
if (argc < 3)
usage(argv[0]);
if (!strcasecmp(argv[1], "compress"))
mode = COMPRESS;
else if (!strcasecmp(argv[1], "decompress"))
mode = DECOMPRESS;
else
usage(argv[0]);
for (argn = 2; argn < argc; argn++) {
arg = argv[argn];
if (*arg != '-') {
filename = arg;
/* Not a switch, must be a file name argument */
break; /* done parsing switches */
}
arg++; /* advance past switch marker character */
if (!strncasecmp(arg, "p", 1)) {
/* Set data precision. */
if (++argn >= argc) /* advance to next argument */
usage(argv[0]);
if (sscanf(argv[argn], "%d", &data_precision) < 1 ||
(data_precision != 8 && data_precision != 12))
usage(argv[0]);
} else if (!strncasecmp(arg, "q", 1)) {
/* Quality rating (quantization table scaling factor). */
if (++argn >= argc) /* advance to next argument */
usage(argv[0]);
if (sscanf(argv[argn], "%d", &quality) < 1 || quality < 0 ||
quality > 100)
usage(argv[0]);
if (quality < 1)
quality = 1;
}
}
if (!filename)
usage(argv[0]);
if (mode == COMPRESS)
write_JPEG_file(filename, quality, data_precision);
else if (mode == DECOMPRESS) {
if (argc - argn < 2)
usage(argv[0]);
read_JPEG_file(argv[argn], argv[argn + 1]);
}
return 0;
}