# dlib C++ Library - wrppm.c

    /*
     * wrppm.c
     *
     * Copyright (C) 1991-1996, Thomas G. Lane.
     * Modified 2009 by Guido Vollbeding.
     * This file is part of the Independent JPEG Group's software.
     * For conditions of distribution and use, see the accompanying README file.
     *
     * This file contains routines to write output images in PPM/PGM format.
     * The extended 2-byte-per-sample raw PPM/PGM formats are supported.
     * The PBMPLUS library is NOT required to compile this software
     * (but it is highly useful as a set of PPM image manipulation programs).
     *
     * These routines may need modification for non-Unix environments or
     * specialized applications.  As they stand, they assume output to
     * an ordinary stdio stream.
     */

    #include "cdjpeg.h"		/* Common decls for cjpeg/djpeg applications */

    #ifdef PPM_SUPPORTED

    /*
     * For 12-bit JPEG data, we either downscale the values to 8 bits
     * (to write standard byte-per-sample PPM/PGM files), or output
     * nonstandard word-per-sample PPM/PGM files.  Downscaling is done
     * if PPM_NORAWWORD is defined (this can be done in the Makefile
     * or in jconfig.h).
     * (When the core library supports data precision reduction, a cleaner
     * implementation will be to ask for that instead.)
     */

    #if BITS_IN_JSAMPLE == 8
    #define PUTPPMSAMPLE(ptr,v)  *ptr++ = (char) (v)
    #define BYTESPERSAMPLE 1
    #define PPM_MAXVAL 255
    #else
    #ifdef PPM_NORAWWORD
    #define PUTPPMSAMPLE(ptr,v)  *ptr++ = (char) ((v) >> (BITS_IN_JSAMPLE-8))
    #define BYTESPERSAMPLE 1
    #define PPM_MAXVAL 255
    #else
    /* The word-per-sample format always puts the MSB first. */
    #define PUTPPMSAMPLE(ptr,v)			\
    	{ register int val_ = v;		\
    	  *ptr++ = (char) ((val_ >> 8) & 0xFF);	\
    	  *ptr++ = (char) (val_ & 0xFF);	\
    	}
    #define BYTESPERSAMPLE 2
    #define PPM_MAXVAL ((1<<BITS_IN_JSAMPLE)-1)
    #endif
    #endif

    /*
     * When JSAMPLE is the same size as char, we can just fwrite() the
     * decompressed data to the PPM or PGM file.  On PCs, in order to make this
     * work the output buffer must be allocated in near data space, because we are
     * assuming small-data memory model wherein fwrite() can't reach far memory.
     * If you need to process very wide images on a PC, you might have to compile
     * in large-memory model, or else replace fwrite() with a putc() loop ---
     * which will be much slower.
     */

    /* Private version of data destination object */

    typedef struct {
      struct djpeg_dest_struct pub;	/* public fields */

      /* Usually these two pointers point to the same place: */
      char *iobuffer;		/* fwrite's I/O buffer */
      JSAMPROW pixrow;		/* decompressor output buffer */
      size_t buffer_width;		/* width of I/O buffer */
      JDIMENSION samples_per_row;	/* JSAMPLEs per output row */
    } ppm_dest_struct;

    typedef ppm_dest_struct * ppm_dest_ptr;

    /*
     * Write some pixel data.
     * In this module rows_supplied will always be 1.
     *
     * put_pixel_rows handles the "normal" 8-bit case where the decompressor
     * output buffer is physically the same as the fwrite buffer.
     */

    METHODDEF(void)
    put_pixel_rows (j_decompress_ptr cinfo, djpeg_dest_ptr dinfo,
    		JDIMENSION rows_supplied)
    {
      ppm_dest_ptr dest = (ppm_dest_ptr) dinfo;

      (void) JFWRITE(dest->pub.output_file, dest->iobuffer, dest->buffer_width);
    }

    /*
     * This code is used when we have to copy the data and apply a pixel
     * format translation.  Typically this only happens in 12-bit mode.
     */

    METHODDEF(void)
    copy_pixel_rows (j_decompress_ptr cinfo, djpeg_dest_ptr dinfo,
    		 JDIMENSION rows_supplied)
    {
      ppm_dest_ptr dest = (ppm_dest_ptr) dinfo;
      register char * bufferptr;
      register JSAMPROW ptr;
      register JDIMENSION col;

      ptr = dest->pub.buffer[0];
      bufferptr = dest->iobuffer;
      for (col = dest->samples_per_row; col > 0; col--) {
        PUTPPMSAMPLE(bufferptr, GETJSAMPLE(*ptr++));
      }
      (void) JFWRITE(dest->pub.output_file, dest->iobuffer, dest->buffer_width);
    }

    /*
     * Write some pixel data when color quantization is in effect.
     * We have to demap the color index values to straight data.
     */

    METHODDEF(void)
    put_demapped_rgb (j_decompress_ptr cinfo, djpeg_dest_ptr dinfo,
    		  JDIMENSION rows_supplied)
    {
      ppm_dest_ptr dest = (ppm_dest_ptr) dinfo;
      register char * bufferptr;
      register int pixval;
      register JSAMPROW ptr;
      register JSAMPROW color_map0 = cinfo->colormap[0];
      register JSAMPROW color_map1 = cinfo->colormap[1];
      register JSAMPROW color_map2 = cinfo->colormap[2];
      register JDIMENSION col;

      ptr = dest->pub.buffer[0];
      bufferptr = dest->iobuffer;
      for (col = cinfo->output_width; col > 0; col--) {
        pixval = GETJSAMPLE(*ptr++);
        PUTPPMSAMPLE(bufferptr, GETJSAMPLE(color_map0[pixval]));
        PUTPPMSAMPLE(bufferptr, GETJSAMPLE(color_map1[pixval]));
        PUTPPMSAMPLE(bufferptr, GETJSAMPLE(color_map2[pixval]));
      }
      (void) JFWRITE(dest->pub.output_file, dest->iobuffer, dest->buffer_width);
    }

    METHODDEF(void)
    put_demapped_gray (j_decompress_ptr cinfo, djpeg_dest_ptr dinfo,
    		   JDIMENSION rows_supplied)
    {
      ppm_dest_ptr dest = (ppm_dest_ptr) dinfo;
      register char * bufferptr;
      register JSAMPROW ptr;
      register JSAMPROW color_map = cinfo->colormap[0];
      register JDIMENSION col;

      ptr = dest->pub.buffer[0];
      bufferptr = dest->iobuffer;
      for (col = cinfo->output_width; col > 0; col--) {
        PUTPPMSAMPLE(bufferptr, GETJSAMPLE(color_map[GETJSAMPLE(*ptr++)]));
      }
      (void) JFWRITE(dest->pub.output_file, dest->iobuffer, dest->buffer_width);
    }

    /*
     * Startup: write the file header.
     */

    METHODDEF(void)
    start_output_ppm (j_decompress_ptr cinfo, djpeg_dest_ptr dinfo)
    {
      ppm_dest_ptr dest = (ppm_dest_ptr) dinfo;

      /* Emit file header */
      switch (cinfo->out_color_space) {
      case JCS_GRAYSCALE:
        /* emit header for raw PGM format */
        fprintf(dest->pub.output_file, "P5\n%ld %ld\n%d\n",
    	    (long) cinfo->output_width, (long) cinfo->output_height,
    	    PPM_MAXVAL);
        break;
      case JCS_RGB:
        /* emit header for raw PPM format */
        fprintf(dest->pub.output_file, "P6\n%ld %ld\n%d\n",
    	    (long) cinfo->output_width, (long) cinfo->output_height,
    	    PPM_MAXVAL);
        break;
      default:
        ERREXIT(cinfo, JERR_PPM_COLORSPACE);
      }
    }

    /*
     * Finish up at the end of the file.
     */

    METHODDEF(void)
    finish_output_ppm (j_decompress_ptr cinfo, djpeg_dest_ptr dinfo)
    {
      /* Make sure we wrote the output file OK */
      fflush(dinfo->output_file);
      if (ferror(dinfo->output_file))
        ERREXIT(cinfo, JERR_FILE_WRITE);
    }

    /*
     * The module selection routine for PPM format output.
     */

    GLOBAL(djpeg_dest_ptr)
    jinit_write_ppm (j_decompress_ptr cinfo)
    {
      ppm_dest_ptr dest;

      /* Create module interface object, fill in method pointers */
      dest = (ppm_dest_ptr)
          (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
    				  SIZEOF(ppm_dest_struct));
      dest->pub.start_output = start_output_ppm;
      dest->pub.finish_output = finish_output_ppm;

      /* Calculate output image dimensions so we can allocate space */
      jpeg_calc_output_dimensions(cinfo);

      /* Create physical I/O buffer.  Note we make this near on a PC. */
      dest->samples_per_row = cinfo->output_width * cinfo->out_color_components;
      dest->buffer_width = dest->samples_per_row * (BYTESPERSAMPLE * SIZEOF(char));
      dest->iobuffer = (char *) (*cinfo->mem->alloc_small)
        ((j_common_ptr) cinfo, JPOOL_IMAGE, dest->buffer_width);

      if (cinfo->quantize_colors || BITS_IN_JSAMPLE != 8 ||
          SIZEOF(JSAMPLE) != SIZEOF(char)) {
        /* When quantizing, we need an output buffer for colormap indexes
         * that's separate from the physical I/O buffer.  We also need a
         * separate buffer if pixel format translation must take place.
         */
        dest->pub.buffer = (*cinfo->mem->alloc_sarray)
          ((j_common_ptr) cinfo, JPOOL_IMAGE,
           cinfo->output_width * cinfo->output_components, (JDIMENSION) 1);
        dest->pub.buffer_height = 1;
        if (! cinfo->quantize_colors)
          dest->pub.put_pixel_rows = copy_pixel_rows;
        else if (cinfo->out_color_space == JCS_GRAYSCALE)
          dest->pub.put_pixel_rows = put_demapped_gray;
        else
          dest->pub.put_pixel_rows = put_demapped_rgb;
      } else {
        /* We will fwrite() directly from decompressor output buffer. */
        /* Synthesize a JSAMPARRAY pointer structure */
        /* Cast here implies near->far pointer conversion on PCs */
        dest->pixrow = (JSAMPROW) dest->iobuffer;
        dest->pub.buffer = & dest->pixrow;
        dest->pub.buffer_height = 1;
        dest->pub.put_pixel_rows = put_pixel_rows;
      }

      return (djpeg_dest_ptr) dest;
    }

    #endif /* PPM_SUPPORTED */