203 lines
6.8 KiB
C
203 lines
6.8 KiB
C
/* Just a part of the lowres functionality. It has to be in a separate
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file, otherwise the data destination manager routines would conflict
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with the ones used for decompression. Someone needs to write an
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object-oriented extension for C. ;-)))
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*/
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#ifdef __cplusplus
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extern "C" {
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#endif
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#include "jinclude.h"
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#include "jpeglib.h"
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#include "jerror.h"
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/* YANNIS: This _fine_ library wants me to define a data destination
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manager just to be able to write compressed data in memory. */
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typedef struct {
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struct jpeg_destination_mgr pub; /* public fields */
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size_t total_size;
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JOCTET * output; /* target stream */
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} my_destination_mgr;
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typedef my_destination_mgr * my_dest_ptr;
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METHODDEF(void)
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init_destination (j_compress_ptr cinfo)
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{
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my_dest_ptr this_obj = (my_dest_ptr) cinfo->dest;
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this_obj->total_size = cinfo->image_width * cinfo->input_components *
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cinfo->image_height;
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/* Probably too much space, but let's be conservative */
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this_obj->output = (JOCTET *) malloc(this_obj->total_size * sizeof(JOCTET));
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this_obj->pub.next_output_byte = this_obj->output;
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this_obj->pub.free_in_buffer = this_obj->total_size;
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}
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/* The following routine contributed by Ilya Bagrak (Spring'03) */
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METHODDEF(boolean)
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empty_output_buffer (j_compress_ptr cinfo)
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{
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my_dest_ptr dest = (my_dest_ptr) cinfo->dest;
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unsigned char* ret;
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ret = realloc(dest->output, dest->total_size + 1024);
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dest->output = ret;
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dest->total_size += 1024;
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dest->pub.next_output_byte = dest->output + dest->total_size - 1024;
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dest->pub.free_in_buffer = 1024;
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fprintf(stderr, "ASSERTION FAILURE\n");
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return TRUE; /* This shouldn't happen */
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}
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/*
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* Terminate destination --- called by jpeg_finish_compress
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* after all data has been written. Usually needs to flush buffer.
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*/
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METHODDEF(void)
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term_destination (j_compress_ptr cinfo)
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{
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return; /* No need to do anything */
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}
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GLOBAL(void)
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jpeg_mem_dest (j_compress_ptr cinfo)
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{
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my_dest_ptr dest;
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if (cinfo->dest == NULL) { /* first time for this JPEG object? */
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cinfo->dest = (struct jpeg_destination_mgr *)
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(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
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SIZEOF(my_destination_mgr));
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}
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dest = (my_dest_ptr) cinfo->dest;
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dest->pub.init_destination = init_destination;
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dest->pub.empty_output_buffer = empty_output_buffer;
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dest->pub.term_destination = term_destination;
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}
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GLOBAL(void)
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write_JPEG_file (JSAMPARRAY buffer, int image_width, int image_height,
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int color_comp, J_COLOR_SPACE color_space,
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int quality, JOCTET **output, int *output_size)
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{
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/* This struct contains the JPEG compression parameters and pointers to
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* working space (which is allocated as needed by the JPEG library).
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* It is possible to have several such structures, representing multiple
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* compression/decompression processes, in existence at once. We refer
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* to any one struct (and its associated working data) as a "JPEG object".
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*/
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struct jpeg_compress_struct cinfo;
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/* This struct represents a JPEG error handler. It is declared separately
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* because applications often want to supply a specialized error handler
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* (see the second half of this file for an example). But here we just
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* take the easy way out and use the standard error handler, which will
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* print a message on stderr and call exit() if compression fails.
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* Note that this struct must live as long as the main JPEG parameter
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* struct, to avoid dangling-pointer problems.
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*/
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struct jpeg_error_mgr jerr;
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/* More stuff */
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JSAMPROW row_pointer[1]; /* pointer to JSAMPLE row[s] */
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int row_stride; /* physical row width in image buffer */
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/* Step 1: allocate and initialize JPEG compression object */
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/* We have to set up the error handler first, in case the initialization
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* step fails. (Unlikely, but it could happen if you are out of memory.)
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* This routine fills in the contents of struct jerr, and returns jerr's
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* address which we place into the link field in cinfo.
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*/
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cinfo.err = jpeg_std_error(&jerr);
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/* Now we can initialize the JPEG compression object. */
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jpeg_create_compress(&cinfo);
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/* Step 2: set parameters for compression */
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/* First we supply a description of the input image.
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* Four fields of the cinfo struct must be filled in:
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*/
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cinfo.image_width = image_width; /* image width and height, in pixels */
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cinfo.image_height = image_height;
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cinfo.input_components = color_comp; /* # of color components per pixel */
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cinfo.in_color_space = color_space; /* colorspace of input image */
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/* Step 3: specify data destination (eg, a file) */
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jpeg_mem_dest(&cinfo);
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/* Now use the library's routine to set default compression parameters.
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* (You must set at least cinfo.in_color_space before calling this,
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* since the defaults depend on the source color space.)
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*/
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jpeg_set_defaults(&cinfo);
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/* Now you can set any non-default parameters you wish to.
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* Here we just illustrate the use of quality (quantization table) scaling:
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*/
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jpeg_set_quality(&cinfo, quality, TRUE /* limit to baseline-JPEG values */);
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/* Step 4: Start compressor */
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/* TRUE ensures that we will write a complete interchange-JPEG file.
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* Pass TRUE unless you are very sure of what you're doing.
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*/
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jpeg_start_compress(&cinfo, TRUE);
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/* Step 5: while (scan lines remain to be written) */
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/* jpeg_write_scanlines(...); */
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/* Here we use the library's state variable cinfo.next_scanline as the
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* loop counter, so that we don't have to keep track ourselves.
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* To keep things simple, we pass one scanline per call; you can pass
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* more if you wish, though.
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*/
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row_stride = image_width * 3; /* JSAMPLEs per row in image_buffer */
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while (cinfo.next_scanline < cinfo.image_height) {
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/* jpeg_write_scanlines expects an array of pointers to scanlines.
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* Here the array is only one element long, but you could pass
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* more than one scanline at a time if that's more convenient.
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*/
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row_pointer[0] = buffer[cinfo.next_scanline];
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(void) jpeg_write_scanlines(&cinfo, row_pointer, 1);
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}
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/* Step 6: Finish compression */
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jpeg_finish_compress(&cinfo);
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{
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my_dest_ptr this_obj = (my_dest_ptr) cinfo.dest;
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*output = this_obj->output;
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*output_size = this_obj->total_size - this_obj->pub.free_in_buffer;
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/* We destroy that pointer so that it is not used to deallocate the
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output data */
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this_obj->output = NULL;
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}
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/* Step 7: release JPEG compression object */
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/* This is an important step since it will release a good deal of memory. */
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jpeg_destroy_compress(&cinfo);
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/* And we're done! */
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}
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#ifdef __cplusplus
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}
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#endif
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