value dGifGetLine( value hdl )
{
CAMLparam1(hdl);
CAMLlocal1(buf);
GifFileType *GifFile = (GifFileType*) hdl;
if( oversized( GifFile->Image.Width, sizeof(GifPixelType) ) ){
failwith_oversized("gif");
}
buf = alloc_string( GifFile->Image.Width * sizeof(GifPixelType) );
if( DGifGetLine(GifFile, String_val(buf), GifFile->Image.Width )
== GIF_ERROR ){
// PrintGifError ();
failwith("DGifGetLine");
}
CAMLreturn(buf);
}
read_JPEG_file (value name)
{
CAMLparam1(name);
CAMLlocal1(res);
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 */
int i;
filename= String_val( name );
/* 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) {
failwith("failed to open jpeg file");
}
/* 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.
*/
fprintf(stderr, "Exiting...");
jpeg_destroy_decompress(&cinfo);
fclose(infile);
exit(-1);
failwith(jpg_error_message);
}
/* 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.doc 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.
*/
cinfo.out_color_space = JCS_RGB;
/* 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 */
if( oversized(cinfo.output_width, cinfo.output_components) ){
jpeg_destroy_decompress(&cinfo);
fclose(infile);
failwith_oversized("jpeg");
}
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,
cinfo.output_height );
/* 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.
*/
jpeg_read_scanlines(&cinfo, buffer + cinfo.output_scanline, 1);
}
if( oversized(row_stride, cinfo.output_height) ){
jpeg_destroy_decompress(&cinfo);
fclose(infile);
failwith_oversized("jpeg");
}
{
CAMLlocalN(r,3);
r[0] = Val_int(cinfo.output_width);
r[1] = Val_int(cinfo.output_height);
r[2] = alloc_string ( row_stride * cinfo.output_height );
for(i=0; i<cinfo.output_height; i++){
memcpy( String_val(r[2]) + i * row_stride,
buffer[i], row_stride);
}
res = alloc_tuple(3);
for(i=0; i<3; i++) Field(res, i) = r[i];
}
/* 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! */
CAMLreturn(res);
}
