FCL/sf/mw/qt: comparison src/3rdparty/libjpeg/example.c

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+/*
+* example.c
+*
+* This file illustrates how to use the IJG code as a subroutine library
+* to read or write JPEG image files.  You should look at this code in
+* conjunction with the documentation file libjpeg.txt.
+*
+* This code will not do anything useful as-is, but it may be helpful as a
+* skeleton for constructing routines that call the JPEG library.
+*
+* 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.
+*/
+#include <stdio.h>
+/*
+* 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"
+/*
+* <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).
+* 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:
+*/
+extern JSAMPLE * image_buffer;	/* Points to large array of R,G,B-order data */
+extern int image_height;	/* Number of rows in image */
+extern int image_width;		/* Number of columns in image */
+/*
+* Sample routine for JPEG compression.  We assume that the target file name
+* and a compression quality factor are passed in.
+*/
+GLOBAL(void)
+write_JPEG_file (char * filename, int quality)
+{
+/* 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 */
+JSAMPROW row_pointer[1];	/* pointer to JSAMPLE row[s] */
+int row_stride;		/* physical row width in image buffer */
+/* 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) {
+fprintf(stderr, "can't open %s\n", filename);
+exit(1);
+}
+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 = image_width; 	/* image width and height, in pixels */
+cinfo.image_height = image_height;
+cinfo.input_components = 3;		/* # of color components per pixel */
+cinfo.in_color_space = JCS_RGB; 	/* colorspace 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 */);
+/* 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: 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.
+*/
+row_stride = image_width * 3;	/* JSAMPLEs per row in image_buffer */
+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 * row_stride];
+(void) jpeg_write_scanlines(&cinfo, row_pointer, 1);
+}
+/* Step 6: Finish compression */
+jpeg_finish_compress(&cinfo);
+/* After finish_compress, we can close the output file. */
+fclose(outfile);
+/* Step 7: 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 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);
+}
+/*
+* 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.
+*/
+GLOBAL(int)
+read_JPEG_file (char * filename)
+{
+/* 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;
+/* 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 */
+JSAMPARRAY buffer;		/* Output row buffer */
+int row_stride;		/* physical row width in output buffer */
+/* In this example we want to open the input file before doing anything else,
+* so that the setjmp() error recovery below can assume the file is open.
+* VERY IMPORTANT: use "b" option to fopen() if you are on a machine that
+* requires it in order to read binary files.
+*/
+if ((infile = fopen(filename, "rb")) == NULL) {
+fprintf(stderr, "can't open %s\n", filename);
+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);
+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.
+*/
+/* 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.
+*/
+/* JSAMPLEs 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 */
+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.
+*/
+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);
+/* 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);
+/* 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 file.
+* 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);
+/* 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.
+*/