The Independent JPEG Group's JPEG software v5

wrppm.c

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+/*
+ * wrppm.c
+ *
+ * Copyright (C) 1991-1994, Thomas G. Lane.
+ * 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 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
+
+
+/*
+ * Currently, this code only knows how to write raw PPM or PGM format,
+ * which can be no more than 8 bits/sample.  As an expedient for testing
+ * 12-bit JPEG mode, we support writing 12-bit data to an 8-bit file by
+ * downscaling the values.  Of course this implies loss of precision.
+ * (When the core library supports data precision reduction, a cleaner
+ * implementation will be to ask for that instead.)
+ */
+
+#if BITS_IN_JSAMPLE == 8
+#define DOWNSCALE(x)  (x)
+#else
+#define DOWNSCALE(x)  ((x) >> (BITS_IN_JSAMPLE-8))
+#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 */
+
+  JDIMENSION buffer_width;	/* width of one 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 because JSAMPLE is not
+ * the same size as char.  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->buffer_width; col > 0; col--) {
+    *bufferptr++ = (char) DOWNSCALE(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++);
+    *bufferptr++ = (char) DOWNSCALE(GETJSAMPLE(color_map0[pixval]));
+    *bufferptr++ = (char) DOWNSCALE(GETJSAMPLE(color_map1[pixval]));
+    *bufferptr++ = (char) DOWNSCALE(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--) {
+    *bufferptr++ = (char) DOWNSCALE(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, 255);
+    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, 255);
+    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->buffer_width = cinfo->output_width * cinfo->out_color_components;
+  dest->iobuffer = (char *)
+    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
+				(size_t) (dest->buffer_width * SIZEOF(char)));
+
+  if (cinfo->quantize_colors || 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 JSAMPLE and char are not the same size.
+     */
+    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 */