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); }