/*
 * djpeg.c
 *
 * This file was part of the Independent JPEG Group's software:
 * Copyright (C) 1991-1997, Thomas G. Lane.
 * Modified 2013 by Guido Vollbeding.
 * libjpeg-turbo Modifications:
 * Copyright (C) 2010-2011, 2013-2016, D. R. Commander.
 * Copyright (C) 2015, Google, Inc.
 * For conditions of distribution and use, see the accompanying README.ijg
 * file.
 *
 * This file contains a command-line user interface for the JPEG decompressor.
 * It should work on any system with Unix- or MS-DOS-style command lines.
 *
 * Two different command line styles are permitted, depending on the
 * compile-time switch TWO_FILE_COMMANDLINE:
 *      djpeg [options]  inputfile outputfile
 *      djpeg [options]  [inputfile]
 * In the second style, output is always to standard output, which you'd
 * normally redirect to a file or pipe to some other program.  Input is
 * either from a named file or from standard input (typically redirected).
 * The second style is convenient on Unix but is unhelpful on systems that
 * don't support pipes.  Also, you MUST use the first style if your system
 * doesn't do binary I/O to stdin/stdout.
 * To simplify script writing, the "-outfile" switch is provided.  The syntax
 *      djpeg [options]  -outfile outputfile  inputfile
 * works regardless of which command line style is used.
 */

#include "cdjpeg.h"             /* Common decls for cjpeg/djpeg applications */
#include "jversion.h"           /* for version message */
#include "jconfigint.h"
#include "wrppm.h"

#include <ctype.h>              /* to declare isprint() */

#ifdef USE_CCOMMAND             /* command-line reader for Macintosh */
#ifdef __MWERKS__
#include <SIOUX.h>              /* Metrowerks needs this */
#include <console.h>            /* ... and this */
#endif
#ifdef THINK_C
#include <console.h>            /* Think declares it here */
#endif
#endif


/* Create the add-on message string table. */

#define JMESSAGE(code, string)   string ,

static const char *const cdjpeg_message_table[] = {
#include "cderror.h"

		NULL
};


/*
 * This list defines the known output image formats
 * (not all of which need be supported by a given version).
 * You can change the default output format by defining DEFAULT_FMT;
 * indeed, you had better do so if you undefine PPM_SUPPORTED.
 */

typedef enum {
	FMT_BMP,                /* BMP format (Windows flavor) */
	FMT_GIF,                /* GIF format */
	FMT_OS2,                /* BMP format (OS/2 flavor) */
	FMT_PPM,                /* PPM/PGM (PBMPLUS formats) */
	FMT_RLE,                /* RLE format */
	FMT_TARGA,              /* Targa format */
	FMT_TIFF                /* TIFF format */
} IMAGE_FORMATS;

#ifndef DEFAULT_FMT             /* so can override from CFLAGS in Makefile */
#define DEFAULT_FMT     FMT_PPM
#endif

static IMAGE_FORMATS requested_fmt;


/*
 * Argument-parsing code.
 * The switch parser is designed to be useful with DOS-style command line
 * syntax, ie, intermixed switches and file names, where only the switches
 * to the left of a given file name affect processing of that file.
 * The main program in this file doesn't actually use this capability...
 */


static const char *progname;    /* program name for error messages */
static char *outfilename;       /* for -outfile switch */
boolean memsrc;                 /* for -memsrc switch */
boolean skip, crop;
JDIMENSION skip_start, skip_end;
JDIMENSION crop_x, crop_y, crop_width, crop_height;
#define INPUT_BUF_SIZE  4096


LOCAL(void)
usage(void)
/* complain about bad command line */
{
	fprintf(stderr, "usage: %s [switches] ", progname);
#ifdef TWO_FILE_COMMANDLINE
	fprintf(stderr, "inputfile outputfile\n");
#else
	fprintf(stderr, "[inputfile]\n");
#endif

	fprintf(stderr, "Switches (names may be abbreviated):\n");
	fprintf(stderr, "  -colors N      Reduce image to no more than N colors\n");
	fprintf(stderr, "  -fast          Fast, low-quality processing\n");
	fprintf(stderr, "  -grayscale     Force grayscale output\n");
	fprintf(stderr, "  -rgb           Force RGB output\n");
	fprintf(stderr, "  -rgb565        Force RGB565 output\n");
#ifdef IDCT_SCALING_SUPPORTED
	fprintf(stderr, "  -scale M/N     Scale output image by fraction M/N, eg, 1/8\n");
#endif
#ifdef BMP_SUPPORTED
	fprintf(stderr, "  -bmp           Select BMP output format (Windows style)%s\n",
			(DEFAULT_FMT == FMT_BMP ? " (default)" : ""));
#endif
#ifdef GIF_SUPPORTED
	fprintf(stderr, "  -gif           Select GIF output format%s\n",
			(DEFAULT_FMT == FMT_GIF ? " (default)" : ""));
#endif
#ifdef BMP_SUPPORTED
	fprintf(stderr, "  -os2           Select BMP output format (OS/2 style)%s\n",
			(DEFAULT_FMT == FMT_OS2 ? " (default)" : ""));
#endif
#ifdef PPM_SUPPORTED
	fprintf(stderr, "  -pnm           Select PBMPLUS (PPM/PGM) output format%s\n",
			(DEFAULT_FMT == FMT_PPM ? " (default)" : ""));
#endif
#ifdef RLE_SUPPORTED
	fprintf(stderr, "  -rle           Select Utah RLE output format%s\n",
			(DEFAULT_FMT == FMT_RLE ? " (default)" : ""));
#endif
#ifdef TARGA_SUPPORTED
	fprintf(stderr, "  -targa         Select Targa output format%s\n",
			(DEFAULT_FMT == FMT_TARGA ? " (default)" : ""));
#endif
	fprintf(stderr, "Switches for advanced users:\n");
#ifdef DCT_ISLOW_SUPPORTED
	fprintf(stderr, "  -dct int       Use integer DCT method%s\n",
	        (JDCT_DEFAULT == JDCT_ISLOW ? " (default)" : ""));
#endif
#ifdef DCT_IFAST_SUPPORTED
	fprintf(stderr, "  -dct fast      Use fast integer DCT (less accurate)%s\n",
	        (JDCT_DEFAULT == JDCT_IFAST ? " (default)" : ""));
#endif
#ifdef DCT_FLOAT_SUPPORTED
	fprintf(stderr, "  -dct float     Use floating-point DCT method%s\n",
	        (JDCT_DEFAULT == JDCT_FLOAT ? " (default)" : ""));
#endif
	fprintf(stderr, "  -dither fs     Use F-S dithering (default)\n");
	fprintf(stderr, "  -dither none   Don't use dithering in quantization\n");
	fprintf(stderr, "  -dither ordered  Use ordered dither (medium speed, quality)\n");
#ifdef QUANT_2PASS_SUPPORTED
	fprintf(stderr, "  -map FILE      Map to colors used in named image file\n");
#endif
	fprintf(stderr, "  -nosmooth      Don't use high-quality upsampling\n");
#ifdef QUANT_1PASS_SUPPORTED
	fprintf(stderr, "  -onepass       Use 1-pass quantization (fast, low quality)\n");
#endif
	fprintf(stderr, "  -maxmemory N   Maximum memory to use (in kbytes)\n");
	fprintf(stderr, "  -outfile name  Specify name for output file\n");
#if JPEG_LIB_VERSION >= 80 || defined(MEM_SRCDST_SUPPORTED)
	fprintf(stderr, "  -memsrc        Load input file into memory before decompressing\n");
#endif

	fprintf(stderr, "  -skip Y0,Y1    Decompress all rows except those between Y0 and Y1 (inclusive)\n");
	fprintf(stderr, "  -crop WxH+X+Y  Decompress only a rectangular subregion of the image\n");
	fprintf(stderr, "  -verbose  or  -debug   Emit debug output\n");
	fprintf(stderr, "  -version       Print version information and exit\n");
	exit(EXIT_FAILURE);
}


LOCAL(int)
parse_switches(j_decompress_ptr cinfo, int argc, char **argv,
               int last_file_arg_seen, boolean for_real)
/* Parse optional switches.
 * Returns argv[] index of first file-name argument (== argc if none).
 * Any file names with indexes <= last_file_arg_seen are ignored;
 * they have presumably been processed in a previous iteration.
 * (Pass 0 for last_file_arg_seen on the first or only iteration.)
 * for_real is FALSE on the first (dummy) pass; we may skip any expensive
 * processing.
 */
{
	int argn;
	char *arg;

	/* Set up default JPEG parameters. */
	requested_fmt = DEFAULT_FMT;  /* set default output file format */
	outfilename = NULL;
	memsrc = FALSE;
	skip = FALSE;
	crop = FALSE;
	cinfo->err->trace_level = 0;

	/* Scan command line options, adjust parameters */

	for (argn = 1; argn < argc; argn++) {
		arg = argv[argn];
		if (*arg != '-') {
			/* Not a switch, must be a file name argument */
			if (argn <= last_file_arg_seen) {
				outfilename = NULL;     /* -outfile applies to just one input file */
				continue;               /* ignore this name if previously processed */
			}
			break;                    /* else done parsing switches */
		}
		arg++;                      /* advance past switch marker character */

		if (keymatch(arg, "bmp", 1)) {
			/* BMP output format. */
			requested_fmt = FMT_BMP;

		} else if (keymatch(arg, "colors", 1) || keymatch(arg, "colours", 1) ||
		           keymatch(arg, "quantize", 1) || keymatch(arg, "quantise", 1)) {
			/* Do color quantization. */
			int val;

			if (++argn >= argc)       /* advance to next argument */
				usage();
			if (sscanf(argv[argn], "%d", &val) != 1)
				usage();
			cinfo->desired_number_of_colors = val;
			cinfo->quantize_colors = TRUE;

		} else if (keymatch(arg, "dct", 2)) {
			/* Select IDCT algorithm. */
			if (++argn >= argc)       /* advance to next argument */
				usage();
			if (keymatch(argv[argn], "int", 1)) {
				cinfo->dct_method = JDCT_ISLOW;
			} else if (keymatch(argv[argn], "fast", 2)) {
				cinfo->dct_method = JDCT_IFAST;
			} else if (keymatch(argv[argn], "float", 2)) {
				cinfo->dct_method = JDCT_FLOAT;
			} else
				usage();

		} else if (keymatch(arg, "dither", 2)) {
			/* Select dithering algorithm. */
			if (++argn >= argc)       /* advance to next argument */
				usage();
			if (keymatch(argv[argn], "fs", 2)) {
				cinfo->dither_mode = JDITHER_FS;
			} else if (keymatch(argv[argn], "none", 2)) {
				cinfo->dither_mode = JDITHER_NONE;
			} else if (keymatch(argv[argn], "ordered", 2)) {
				cinfo->dither_mode = JDITHER_ORDERED;
			} else
				usage();

		} else if (keymatch(arg, "debug", 1) || keymatch(arg, "verbose", 1)) {
			/* Enable debug printouts. */
			/* On first -d, print version identification */
			static boolean printed_version = FALSE;

			if (!printed_version) {
				fprintf(stderr, "%s version %s (build %s)\n",
				        PACKAGE_NAME, VERSION, BUILD);
				fprintf(stderr, "%s\n\n", JCOPYRIGHT);
				fprintf(stderr, "Emulating The Independent JPEG Group's software, version %s\n\n",
				        JVERSION);
				printed_version = TRUE;
			}
			cinfo->err->trace_level++;

		} else if (keymatch(arg, "version", 4)) {
			fprintf(stderr, "%s version %s (build %s)\n",
			        PACKAGE_NAME, VERSION, BUILD);
			exit(EXIT_SUCCESS);

		} else if (keymatch(arg, "fast", 1)) {
			/* Select recommended processing options for quick-and-dirty output. */
			cinfo->two_pass_quantize = FALSE;
			cinfo->dither_mode = JDITHER_ORDERED;
			if (!cinfo->quantize_colors) /* don't override an earlier -colors */
				cinfo->desired_number_of_colors = 216;
			cinfo->dct_method = JDCT_FASTEST;
			cinfo->do_fancy_upsampling = FALSE;

		} else if (keymatch(arg, "gif", 1)) {
			/* GIF output format. */
			requested_fmt = FMT_GIF;

		} else if (keymatch(arg, "grayscale", 2) || keymatch(arg, "greyscale", 2)) {
			/* Force monochrome output. */
			cinfo->out_color_space = JCS_GRAYSCALE;

		} else if (keymatch(arg, "rgb", 2)) {
			/* Force RGB output. */
			cinfo->out_color_space = JCS_RGB;

		} else if (keymatch(arg, "rgb565", 2)) {
			/* Force RGB565 output. */
			cinfo->out_color_space = JCS_RGB565;

		} else if (keymatch(arg, "map", 3)) {
			/* Quantize to a color map taken from an input file. */
			if (++argn >= argc)       /* advance to next argument */
				usage();
			if (for_real) {           /* too expensive to do twice! */
#ifdef QUANT_2PASS_SUPPORTED    /* otherwise can't quantize to supplied map */
				FILE *mapfile;

				if ((mapfile = fopen(argv[argn], READ_BINARY)) == NULL) {
					fprintf(stderr, "%s: can't open %s\n", progname, argv[argn]);
					exit(EXIT_FAILURE);
				}
				read_color_map(cinfo, mapfile);
				fclose(mapfile);
				cinfo->quantize_colors = TRUE;
#else
				ERREXIT(cinfo, JERR_NOT_COMPILED);
#endif
			}

		} else if (keymatch(arg, "maxmemory", 3)) {
			/* Maximum memory in Kb (or Mb with 'm'). */
			long lval;
			char ch = 'x';

			if (++argn >= argc)       /* advance to next argument */
				usage();
			if (sscanf(argv[argn], "%ld%c", &lval, &ch) < 1)
				usage();
			if (ch == 'm' || ch == 'M')
				lval *= 1000L;
			cinfo->mem->max_memory_to_use = lval * 1000L;

		} else if (keymatch(arg, "nosmooth", 3)) {
			/* Suppress fancy upsampling */
			cinfo->do_fancy_upsampling = FALSE;

		} else if (keymatch(arg, "onepass", 3)) {
			/* Use fast one-pass quantization. */
			cinfo->two_pass_quantize = FALSE;

		} else if (keymatch(arg, "os2", 3)) {
			/* BMP output format (OS/2 flavor). */
			requested_fmt = FMT_OS2;

		} else if (keymatch(arg, "outfile", 4)) {
			/* Set output file name. */
			if (++argn >= argc)       /* advance to next argument */
				usage();
			outfilename = argv[argn]; /* save it away for later use */

		} else if (keymatch(arg, "memsrc", 2)) {
			/* Use in-memory source manager */
#if JPEG_LIB_VERSION >= 80 || defined(MEM_SRCDST_SUPPORTED)
			memsrc = TRUE;
#else
			fprintf(stderr, "%s: sorry, in-memory source manager was not compiled in\n",
			        progname);
			exit(EXIT_FAILURE);
#endif

		} else if (keymatch(arg, "pnm", 1) || keymatch(arg, "ppm", 1)) {
			/* PPM/PGM output format. */
			requested_fmt = FMT_PPM;

		} else if (keymatch(arg, "rle", 1)) {
			/* RLE output format. */
			requested_fmt = FMT_RLE;

		} else if (keymatch(arg, "scale", 2)) {
			/* Scale the output image by a fraction M/N. */
			if (++argn >= argc)       /* advance to next argument */
				usage();
			if (sscanf(argv[argn], "%u/%u",
			           &cinfo->scale_num, &cinfo->scale_denom) != 2)
				usage();

		} else if (keymatch(arg, "skip", 2)) {
			if (++argn >= argc)
				usage();
			if (sscanf(argv[argn], "%u,%u", &skip_start, &skip_end) != 2 ||
			    skip_start > skip_end)
				usage();
			skip = TRUE;

		} else if (keymatch(arg, "crop", 2)) {
			char c;
			if (++argn >= argc)
				usage();
			if (sscanf(argv[argn], "%u%c%u+%u+%u", &crop_width, &c, &crop_height,
			           &crop_x, &crop_y) != 5 ||
			    (c != 'X' && c != 'x') || crop_width < 1 || crop_height < 1)
				usage();
			crop = TRUE;

		} else if (keymatch(arg, "targa", 1)) {
			/* Targa output format. */
			requested_fmt = FMT_TARGA;

		} else {
			usage();                  /* bogus switch */
		}
	}

	return argn;                  /* return index of next arg (file name) */
}


/*
 * Marker processor for COM and interesting APPn markers.
 * This replaces the library's built-in processor, which just skips the marker.
 * We want to print out the marker as text, to the extent possible.
 * Note this code relies on a non-suspending data source.
 */

LOCAL(unsigned int)
jpeg_getc(j_decompress_ptr cinfo)
/* Read next byte */
{
	struct jpeg_source_mgr *datasrc = cinfo->src;

	if (datasrc->bytes_in_buffer == 0) {
		if (!(*datasrc->fill_input_buffer)(cinfo))
			ERREXIT(cinfo, JERR_CANT_SUSPEND);
	}
	datasrc->bytes_in_buffer--;
	return GETJOCTET(*datasrc->next_input_byte++);
}


METHODDEF(boolean)
print_text_marker(j_decompress_ptr cinfo) {
	boolean traceit = (cinfo->err->trace_level >= 1);
	long length;
	unsigned int ch;
	unsigned int lastch = 0;

	length = jpeg_getc(cinfo) << 8;
	length += jpeg_getc(cinfo);
	length -= 2;                  /* discount the length word itself */

	if (traceit) {
		if (cinfo->unread_marker == JPEG_COM)
			fprintf(stderr, "Comment, length %ld:\n", (long) length);
		else                        /* assume it is an APPn otherwise */
			fprintf(stderr, "APP%d, length %ld:\n",
			        cinfo->unread_marker - JPEG_APP0, (long) length);
	}

	while (--length >= 0) {
		ch = jpeg_getc(cinfo);
		if (traceit) {
			/* Emit the character in a readable form.
			 * Nonprintables are converted to \nnn form,
			 * while \ is converted to \\.
			 * Newlines in CR, CR/LF, or LF form will be printed as one newline.
			 */
			if (ch == '\r') {
				fprintf(stderr, "\n");
			} else if (ch == '\n') {
				if (lastch != '\r')
					fprintf(stderr, "\n");
			} else if (ch == '\\') {
				fprintf(stderr, "\\\\");
			} else if (isprint(ch)) {
				putc(ch, stderr);
			} else {
				fprintf(stderr, "\\%03o", ch);
			}
			lastch = ch;
		}
	}

	if (traceit)
		fprintf(stderr, "\n");

	return TRUE;
}


/*
 * The main program.
 */

int
main(int argc, char **argv) {
	struct jpeg_decompress_struct cinfo;
	struct jpeg_error_mgr jerr;
#ifdef PROGRESS_REPORT
	struct cdjpeg_progress_mgr progress;
#endif
	int file_index;
	djpeg_dest_ptr dest_mgr = NULL;
	FILE *input_file;
	FILE *output_file;
	unsigned char *inbuffer = NULL;
	unsigned long insize = 0;
	JDIMENSION num_scanlines;

	/* On Mac, fetch a command line. */
#ifdef USE_CCOMMAND
	argc = ccommand(&argv);
#endif

	progname = argv[0];
	if (progname == NULL || progname[0] == 0)
		progname = "djpeg";         /* in case C library doesn't provide it */

	/* Initialize the JPEG decompression object with default error handling. */
	cinfo.err = jpeg_std_error(&jerr);
	jpeg_create_decompress(&cinfo);
	/* Add some application-specific error messages (from cderror.h) */
	jerr.addon_message_table = cdjpeg_message_table;
	jerr.first_addon_message = JMSG_FIRSTADDONCODE;
	jerr.last_addon_message = JMSG_LASTADDONCODE;

	/* Insert custom marker processor for COM and APP12.
	 * APP12 is used by some digital camera makers for textual info,
	 * so we provide the ability to display it as text.
	 * If you like, additional APPn marker types can be selected for display,
	 * but don't try to override APP0 or APP14 this way (see libjpeg.txt).
	 */
	jpeg_set_marker_processor(&cinfo, JPEG_COM, print_text_marker);
	jpeg_set_marker_processor(&cinfo, JPEG_APP0 + 12, print_text_marker);

	/* Scan command line to find file names. */
	/* It is convenient to use just one switch-parsing routine, but the switch
	 * values read here are ignored; we will rescan the switches after opening
	 * the input file.
	 * (Exception: tracing level set here controls verbosity for COM markers
	 * found during jpeg_read_header...)
	 */

	file_index = parse_switches(&cinfo, argc, argv, 0, FALSE);

#ifdef TWO_FILE_COMMANDLINE
	/* Must have either -outfile switch or explicit output file name */
	if (outfilename == NULL) {
	  if (file_index != argc-2) {
		fprintf(stderr, "%s: must name one input and one output file\n",
				progname);
		usage();
	  }
	  outfilename = argv[file_index+1];
	} else {
	  if (file_index != argc-1) {
		fprintf(stderr, "%s: must name one input and one output file\n",
				progname);
		usage();
	  }
	}
#else
	/* Unix style: expect zero or one file name */
	if (file_index < argc - 1) {
		fprintf(stderr, "%s: only one input file\n", progname);
		usage();
	}
#endif /* TWO_FILE_COMMANDLINE */

	/* Open the input file. */
	if (file_index < argc) {
		if ((input_file = fopen(argv[file_index], READ_BINARY)) == NULL) {
			fprintf(stderr, "%s: can't open %s\n", progname, argv[file_index]);
			exit(EXIT_FAILURE);
		}
	} else {
		/* default input file is stdin */
		input_file = read_stdin();
	}

	/* Open the output file. */
	if (outfilename != NULL) {
		if ((output_file = fopen(outfilename, WRITE_BINARY)) == NULL) {
			fprintf(stderr, "%s: can't open %s\n", progname, outfilename);
			exit(EXIT_FAILURE);
		}
	} else {
		/* default output file is stdout */
		output_file = write_stdout();
	}

#ifdef PROGRESS_REPORT
	start_progress_monitor((j_common_ptr) &cinfo, &progress);
#endif

	/* Specify data source for decompression */
#if JPEG_LIB_VERSION >= 80 || defined(MEM_SRCDST_SUPPORTED)
	if (memsrc) {
	  size_t nbytes;
	  do {
		inbuffer = (unsigned char *)realloc(inbuffer, insize + INPUT_BUF_SIZE);
		if (inbuffer == NULL) {
		  fprintf(stderr, "%s: memory allocation failure\n", progname);
		  exit(EXIT_FAILURE);
		}
		nbytes = JFREAD(input_file, &inbuffer[insize], INPUT_BUF_SIZE);
		if (nbytes < INPUT_BUF_SIZE && ferror(input_file)) {
		  if (file_index < argc)
			fprintf(stderr, "%s: can't read from %s\n", progname,
					argv[file_index]);
		  else
			fprintf(stderr, "%s: can't read from stdin\n", progname);
		}
		insize += (unsigned long)nbytes;
	  } while (nbytes == INPUT_BUF_SIZE);
	  fprintf(stderr, "Compressed size:  %lu bytes\n", insize);
	  jpeg_mem_src(&cinfo, inbuffer, insize);
	} else
#endif
	jpeg_stdio_src(&cinfo, input_file);

	/* Read file header, set default decompression parameters */
	(void) jpeg_read_header(&cinfo, TRUE);

	/* Adjust default decompression parameters by re-parsing the options */
	file_index = parse_switches(&cinfo, argc, argv, 0, TRUE);

	/* Initialize the output module now to let it override any crucial
	 * option settings (for instance, GIF wants to force color quantization).
	 */
	switch (requested_fmt) {
#ifdef BMP_SUPPORTED
		case FMT_BMP:
		  dest_mgr = jinit_write_bmp(&cinfo, FALSE);
		  break;
		case FMT_OS2:
		  dest_mgr = jinit_write_bmp(&cinfo, TRUE);
		  break;
#endif
#ifdef GIF_SUPPORTED
		case FMT_GIF:
		  dest_mgr = jinit_write_gif(&cinfo);
		  break;
#endif
#ifdef PPM_SUPPORTED
		case FMT_PPM:
		  dest_mgr = jinit_write_ppm(&cinfo);
		  break;
#endif
#ifdef RLE_SUPPORTED
		case FMT_RLE:
		  dest_mgr = jinit_write_rle(&cinfo);
		  break;
#endif
#ifdef TARGA_SUPPORTED
		case FMT_TARGA:
		  dest_mgr = jinit_write_targa(&cinfo);
		  break;
#endif
		default:
			ERREXIT(&cinfo, JERR_UNSUPPORTED_FORMAT);
			break;
	}
	dest_mgr->output_file = output_file;

	/* Start decompressor */
	(void) jpeg_start_decompress(&cinfo);

	/* Skip rows */
	if (skip) {
		JDIMENSION tmp;

		/* Check for valid skip_end.  We cannot check this value until after
		 * jpeg_start_decompress() is called.  Note that we have already verified
		 * that skip_start <= skip_end.
		 */
		if (skip_end > cinfo.output_height - 1) {
			fprintf(stderr, "%s: skip region exceeds image height %d\n", progname,
			        cinfo.output_height);
			exit(EXIT_FAILURE);
		}

		/* Write output file header.  This is a hack to ensure that the destination
		 * manager creates an output image of the proper size.
		 */
		tmp = cinfo.output_height;
		cinfo.output_height -= (skip_end - skip_start + 1);
		(*dest_mgr->start_output)(&cinfo, dest_mgr);
		cinfo.output_height = tmp;

		/* Process data */
		while (cinfo.output_scanline < skip_start) {
			num_scanlines = jpeg_read_scanlines(&cinfo, dest_mgr->buffer,
			                                    dest_mgr->buffer_height);
			(*dest_mgr->put_pixel_rows)(&cinfo, dest_mgr, num_scanlines);
		}
		jpeg_skip_scanlines(&cinfo, skip_end - skip_start + 1);
		while (cinfo.output_scanline < cinfo.output_height) {
			num_scanlines = jpeg_read_scanlines(&cinfo, dest_mgr->buffer,
			                                    dest_mgr->buffer_height);
			(*dest_mgr->put_pixel_rows)(&cinfo, dest_mgr, num_scanlines);
		}

		/* Decompress a subregion */
	} else if (crop) {
		JDIMENSION tmp;

		/* Check for valid crop dimensions.  We cannot check these values until
		 * after jpeg_start_decompress() is called.
		 */
		if (crop_x + crop_width > cinfo.output_width ||
		    crop_y + crop_height > cinfo.output_height) {
			fprintf(stderr, "%s: crop dimensions exceed image dimensions %d x %d\n",
			        progname, cinfo.output_width, cinfo.output_height);
			exit(EXIT_FAILURE);
		}

		jpeg_crop_scanline(&cinfo, &crop_x, &crop_width);
		((ppm_dest_ptr) dest_mgr)->buffer_width = cinfo.output_width *
		                                          cinfo.out_color_components *
		                                          sizeof(JSAMPLE);

		/* Write output file header.  This is a hack to ensure that the destination
		 * manager creates an output image of the proper size.
		 */
		tmp = cinfo.output_height;
		cinfo.output_height = crop_height;
		(*dest_mgr->start_output)(&cinfo, dest_mgr);
		cinfo.output_height = tmp;

		/* Process data */
		jpeg_skip_scanlines(&cinfo, crop_y);
		while (cinfo.output_scanline < crop_y + crop_height) {
			num_scanlines = jpeg_read_scanlines(&cinfo, dest_mgr->buffer,
			                                    dest_mgr->buffer_height);
			(*dest_mgr->put_pixel_rows)(&cinfo, dest_mgr, num_scanlines);
		}
		jpeg_skip_scanlines(&cinfo, cinfo.output_height - crop_y - crop_height);

		/* Normal full-image decompress */
	} else {
		/* Write output file header */
		(*dest_mgr->start_output)(&cinfo, dest_mgr);

		/* Process data */
		while (cinfo.output_scanline < cinfo.output_height) {
			num_scanlines = jpeg_read_scanlines(&cinfo, dest_mgr->buffer,
			                                    dest_mgr->buffer_height);
			(*dest_mgr->put_pixel_rows)(&cinfo, dest_mgr, num_scanlines);
		}
	}

#ifdef PROGRESS_REPORT
	/* Hack: count final pass as done in case finish_output does an extra pass.
	 * The library won't have updated completed_passes.
	 */
	progress.pub.completed_passes = progress.pub.total_passes;
#endif

	/* Finish decompression and release memory.
	 * I must do it in this order because output module has allocated memory
	 * of lifespan JPOOL_IMAGE; it needs to finish before releasing memory.
	 */
	(*dest_mgr->finish_output)(&cinfo, dest_mgr);
	(void) jpeg_finish_decompress(&cinfo);
	jpeg_destroy_decompress(&cinfo);

	/* Close files, if we opened them */
	if (input_file != stdin)
		fclose(input_file);
	if (output_file != stdout)
		fclose(output_file);

#ifdef PROGRESS_REPORT
	end_progress_monitor((j_common_ptr) &cinfo);
#endif

	if (memsrc && inbuffer != NULL)
		free(inbuffer);

	/* All done. */
	exit(jerr.num_warnings ? EXIT_WARNING : EXIT_SUCCESS);
	return 0;                     /* suppress no-return-value warnings */
}
