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/* read_jfif() converts a JPEG stream to a NeXT raster bitmap.
* front end to Independent JPEG Group's software.
* For conditions of distribution and use, see the accompanying README file.
*/
/*
* Include file for declaring JPEG data structures.
* This file also includes some system headers like <stdio.h>;
* if you prefer, you can include "jconfig.h" and "jpegdata.h" instead.
*/
#include <c.h>
#include <libc.h>
#include "jinclude.h"
#include <streams/streams.h>
/*
* <setjmp.h> is used for the optional error recovery mechanism shown in
* the second part of the example.
*/
#include <setjmp.h>
/*
* These routines replace the default trace/error routines included with the
* JPEG code. The example trace_message routine shown here is actually the
* same as the standard one, but you could modify it if you don't want messages
* sent to stderr. The example error_exit routine is set up to return
* control to read_JPEG_file() rather than calling exit(). You can use the
* same routines for both compression and decompression error recovery.
*/
/* These static variables are needed by the error routines. */
static jmp_buf setjmp_buffer; /* for return to caller */
static external_methods_ptr emethods; /* needed for access to message_parm */
/* This routine is used for any and all trace, debug, or error printouts
* from the JPEG code. The parameter is a printf format string; up to 8
* integer data values for the format string have been stored in the
* message_parm[] field of the external_methods struct.
*/
METHODDEF void
trace_message (const char *msgtext)
{
/*
fprintf(stderr, msgtext,
emethods->message_parm[0], emethods->message_parm[1],
emethods->message_parm[2], emethods->message_parm[3],
emethods->message_parm[4], emethods->message_parm[5],
emethods->message_parm[6], emethods->message_parm[7]);
fprintf(stderr, "\n");*/ /* there is no \n in the format string! */
}
/*
* The error_exit() routine should not return to its caller. The default
* routine calls exit(), but here we assume that we want to return to
* read_JPEG_data, which has set up a setjmp context for the purpose.
* You should make sure that the free_all method is called, either within
* error_exit or after the return to the outer-level routine.
*/
METHODDEF void
error_exit (const char *msgtext)
{
trace_message(msgtext); /* report the error message */
(*emethods->free_all) (); /* clean up memory allocation & temp files */
longjmp(setjmp_buffer, 1); /* return control to outer routine */
}
/*
* To accept the image data from decompression, you must define four routines
* output_init, put_color_map, put_pixel_rows, and output_term.
*
* You must understand the distinction between full color output mode
* (N independent color components) and colormapped output mode (a single
* output component representing an index into a color map). You should use
* colormapped mode to write to a colormapped display screen or output file.
* Colormapped mode is also useful for reducing grayscale output to a small
* number of gray levels: when using the 1-pass quantizer on grayscale data,
* the colormap entries will be evenly spaced from 0 to MAX_JSAMPLE, so you
* can regard the indexes are directly representing gray levels at reduced
* precision. In any other case, you should not depend on the colormap
* entries having any particular order.
* To get colormapped output, set cinfo->quantize_colors to TRUE and set
* cinfo->desired_number_of_colors to the maximum number of entries in the
* colormap. This can be done either in your main routine or in
* d_ui_method_selection. For grayscale quantization, also set
* cinfo->two_pass_quantize to FALSE to ensure the 1-pass quantizer is used
* (presently this is the default, but it may not be so in the future).
*
* The output file writing modules (jwrppm.c, jwrgif.c, jwrtarga.c, etc) may be
* useful examples of what these routines should actually do, although each of
* them is encrusted with a lot of specialized code for its own file format.
*/
METHODDEF void
output_init (decompress_info_ptr cinfo)
/* This routine should do any setup required */
{
/* This routine can initialize for output based on the data passed in cinfo.
* Useful fields include:
* image_width, image_height Pretty obvious, I hope.
* data_precision bits per pixel value; typically 8.
* out_color_space output colorspace previously requested
* color_out_comps number of color components in same
* final_out_comps number of components actually output
* final_out_comps is 1 if quantize_colors is true, else it is equal to
* color_out_comps.
*/
cinfo->output_buffer = cinfo->output_ptr = (unsigned char *)
malloc(cinfo->image_width * cinfo->image_height * cinfo->final_out_comps);
}
/*
* This function is called repeatedly, with a few more rows of pixels supplied
* on each call. With the current JPEG code, some multiple of 8 rows will be
* passed on each call except the last, but it is extremely bad form to depend
* on this. You CAN assume num_rows > 0.
* The data is supplied in top-to-bottom row order (the standard order within
* a JPEG file). If you cannot readily use the data in that order, you'll
* need an intermediate array to hold the image. See jwrrle.c for an example
* of outputting data in bottom-to-top order.
*
* The data is supplied as a 3-D array of JSAMPLEs, indexed as
* JSAMPLE pixel_data[component][row][column]
* where component runs from 0 to cinfo->final_out_comps-1, row runs from 0 to
* num_rows-1, and column runs from 0 to cinfo->image_width-1 (column 0 is
* left edge of image). Note that this is actually an array of pointers to
* pointers to arrays rather than a true 3D array, since C does not support
* variable-size multidimensional arrays.
* JSAMPLE is typically typedef'd as "unsigned char". If you want your code
* to be as portable as the JPEG code proper, you should always access JSAMPLE
* values with the GETJSAMPLE() macro, which will do the right thing if the
* machine has only signed chars.
*
* If quantize_colors is true, then there is only one component, and its values
* are indexes into the previously supplied colormap. Otherwise the values
* are actual data in your selected output colorspace.
*/
METHODDEF void
put_pixel_rows (decompress_info_ptr cinfo, int num_rows, JSAMPIMAGE pixel_data)
/* Write some rows of output data */
{
unsigned char *ptr = cinfo->output_ptr;
register JSAMPROW ptr0, ptr1, ptr2;
register long col;
register int row;
if (cinfo->num_components == 1) {
for (row = 0; row < num_rows; row++) {
ptr0 = pixel_data[0][row];
for (col = 0; col < cinfo->image_width; col++) {
*ptr++ = GETJSAMPLE(*ptr0); ptr0++;
}
}
cinfo->output_ptr = ptr;
return;
} else if (cinfo->num_components == 3) {
for (row = 0; row < num_rows; row++) {
ptr0 = pixel_data[0][row];
ptr1 = pixel_data[1][row];
ptr2 = pixel_data[2][row];
for (col = 0; col < cinfo->image_width; col++) {
*ptr++ = GETJSAMPLE(*ptr0); ptr0++;
*ptr++ = GETJSAMPLE(*ptr1); ptr1++;
*ptr++ = GETJSAMPLE(*ptr2); ptr2++;
}
}
cinfo->output_ptr = ptr;
return;
} else {
fprintf(stderr, "%d is illegal number of color components.\n",
cinfo->num_components);
exit(-1);
}
}
METHODDEF void
output_term (decompress_info_ptr cinfo)
/* Finish up at the end of the output */
{
}
/*
* That's it for the routines that deal with writing the output image.
* Now we have overall control and parameter selection routines.
*/
/*
* This routine gets control after the JPEG file header has been read;
* at this point the image size and colorspace are known.
* The routine must determine what output routines are to be used, and make
* any decompression parameter changes that are desirable. For example,
* if it is found that the JPEG file is grayscale, you might want to do
* things differently than if it is color. You can also delay setting
* quantize_colors and associated options until this point.
*
* j_d_defaults initializes out_color_space to CS_RGB. If you want grayscale
* output you should set out_color_space to CS_GRAYSCALE. Note that you can
* force grayscale output from a color JPEG file (though not vice versa).
*/
METHODDEF void
d_ui_method_selection (decompress_info_ptr cinfo)
{
/* if grayscale input, force grayscale output; */
/* else leave the output colorspace as set by main routine. */
if (cinfo->jpeg_color_space == CS_GRAYSCALE)
cinfo->out_color_space = CS_GRAYSCALE;
/* select output routines */
cinfo->methods->output_init = output_init;
cinfo->methods->put_color_map = NULL;
cinfo->methods->put_pixel_rows = put_pixel_rows;
cinfo->methods->output_term = output_term;
}
/*
* OK, here is the main function that actually causes everything to happen.
* We assume here that the JPEG filename is supplied by the caller of this
* routine, and that all decompression parameters can be default values.
* The routine returns 1 if successful, 0 if not.
*/
/* read_jfif() converts a JPEG stream to NeXT bitmap raster. Also returns
* width, height, bps and spp
*/
void read_jfif(NXStream *stream, unsigned char **data, int *width,
int *height, int *bps, int *spp)
{
/* These three structs contain JPEG parameters and working data.
* They must survive for the duration of parameter setup and one
* call to jpeg_decompress; typically, making them local data in the
* calling routine is the best strategy.
*/
struct decompress_info_struct cinfo;
struct decompress_methods_struct dc_methods;
struct external_methods_struct e_methods;
cinfo.input_file = stream;
/* Initialize the system-dependent method pointers. */
cinfo.methods = &dc_methods; /* links to method structs */
cinfo.emethods = &e_methods;
/* Here we supply our own error handler; compare to use of standard error
* handler in the previous write_JPEG_file example.
*/
emethods = &e_methods; /* save struct addr for possible access */
e_methods.error_exit = error_exit; /* supply error-exit routine */
e_methods.trace_message = trace_message; /* supply trace-message routine */
/* prepare setjmp context for possible exit from error_exit */
if (setjmp(setjmp_buffer)) {
/* If we get here, the JPEG code has signaled an error.
* Memory allocation has already been cleaned up (see free_all call in
* error_exit), but we need to close the input file before returning.
* You might also need to close an output file, etc.
*/
return;
}
/* Here we use the standard memory manager provided with the JPEG code.
* In some cases you might want to replace the memory manager, or at
* least the system-dependent part of it, with your own code.
*/
jselmemmgr(&e_methods); /* select std memory allocation routines */
/* If the decompressor requires full-image buffers (for two-pass color
* quantization or a noninterleaved JPEG file), it will create temporary
* files for anything that doesn't fit within the maximum-memory setting.
* You can change the default maximum-memory setting by changing
* e_methods.max_memory_to_use after jselmemmgr returns.
* On some systems you may also need to set up a signal handler to
* ensure that temporary files are deleted if the program is interrupted.
* (This is most important if you are on MS-DOS and use the jmemdos.c
* memory manager back end; it will try to grab extended memory for
* temp files, and that space will NOT be freed automatically.)
* See jcmain.c or jdmain.c for an example signal handler.
*/
/* Here, set up the pointer to your own routine for post-header-reading
* parameter selection. You could also initialize the pointers to the
* output data handling routines here, if they are not dependent on the
* image type.
*/
dc_methods.d_ui_method_selection = d_ui_method_selection;
/* Set up default decompression parameters. */
j_d_defaults(&cinfo, TRUE);
/* TRUE indicates that an input buffer should be allocated.
* In unusual cases you may want to allocate the input buffer yourself;
* see jddeflts.c for commentary.
*/
/* At this point you can modify the default parameters set by j_d_defaults
* as needed; for example, you can request color quantization or force
* grayscale output. See jdmain.c for examples of what you might change.
*/
/* Set up to read a JFIF or baseline-JPEG file. */
/* This is the only JPEG file format currently supported. */
jselrjfif(&cinfo);
/* Here we go! */
jpeg_decompress(&cinfo);
*data = cinfo.output_buffer;
*width = cinfo.image_width;
*height = cinfo.image_height;
*bps = cinfo.data_precision;
*spp = cinfo.final_out_comps;
/* Note: if you want to decompress more than one image, we recommend you
* repeat this whole routine. You MUST repeat the j_d_defaults()/alter
* parameters/jpeg_decompress() sequence, as some data structures allocated
* in j_d_defaults are freed upon exit from jpeg_decompress.
*/
}
These are the contents of the former NiCE NeXT User Group NeXTSTEP/OpenStep software archive, currently hosted by Netfuture.ch.