1 files changed, 95 insertions, 0 deletions
diff --git a/converter/other/ppmtopgm.c b/converter/other/ppmtopgm.c
new file mode 100644
index 00000000..86e7ae6a
--- /dev/null
+++ b/converter/other/ppmtopgm.c
@@ -0,0 +1,95 @@
+/* ppmtopgm.c - convert a portable pixmap to a portable graymap
+**
+** Copyright (C) 1989 by Jef Poskanzer.
+**
+** Permission to use, copy, modify, and distribute this software and its
+** documentation for any purpose and without fee is hereby granted, provided
+** that the above copyright notice appear in all copies and that both that
+** copyright notice and this permission notice appear in supporting
+** documentation.  This software is provided "as is" without express or
+** implied warranty.
+*/
+
+#include "pm_c_util.h"
+#include "ppm.h"
+#include "pgm.h"
+#include "lum.h"
+
+static void
+convertRaster(FILE *       const ifP,
+              unsigned int const cols,
+              unsigned int const rows,
+              pixval       const maxval,
+              int          const format, 
+              pixel *      const inputRow,
+              gray *       const outputRow, 
+              FILE *       const ofP) {
+
+    unsigned int row;
+
+    for (row = 0; row < rows; ++row) {
+        ppm_readppmrow( ifP, inputRow, cols, maxval, format );
+        if (maxval <= 255) {
+            /* Use fast approximation to 0.299 r + 0.587 g + 0.114 b */
+            unsigned int col;
+            for (col = 0; col < cols; ++col)
+                outputRow[col] = (gray) ppm_fastlumin(inputRow[col]);
+        } else {
+            /* Can't use fast approximation, so fall back on floats. */
+            int col;
+            for (col = 0; col < cols; ++col) 
+                outputRow[col] = (gray) (PPM_LUMIN(inputRow[col]) + 0.5);
+        }
+        pgm_writepgmrow(ofP, outputRow, cols, maxval, 0);
+    }
+}
+
+
+
+int
+main(int argc, char *argv[]) {
+
+    FILE* ifP;
+    const char * inputFilespec;
+    int eof;
+    
+    ppm_init( &argc, argv );
+
+    if (argc-1 > 1)
+        pm_error("The only argument is the (optional) input filename");
+
+    if (argc == 2)
+        inputFilespec = argv[1];
+    else
+        inputFilespec = "-";
+    
+    ifP = pm_openr(inputFilespec);
+
+    eof = FALSE;  /* initial assumption */
+
+    while (!eof) {
+        ppm_nextimage(ifP, &eof);
+        if (!eof) {
+            int rows, cols, format;
+            pixval maxval;
+            pixel* inputRow;
+            gray* outputRow;
+
+            ppm_readppminit(ifP, &cols, &rows, &maxval, &format);
+            pgm_writepgminit(stdout, cols, rows, maxval, 0);
+
+            inputRow = ppm_allocrow(cols);
+            outputRow = pgm_allocrow(cols);
+
+            convertRaster(ifP, cols, rows, maxval, format, 
+                          inputRow, outputRow, stdout);
+
+            ppm_freerow(inputRow);
+            pgm_freerow(outputRow);
+        }
+    }
+    pm_close(ifP);
+    pm_close(stdout);
+
+    return 0;
+}