Add parameter in compresspdf to control the resolution of the wrapped…

… image

* The page image is assumed to have a maximum dimension of either
  about 1650 or 3300 pixels, depending on whether this parameter
  is 150 ppi (default) or 300 ppi.

prog/compresspdf.c

@@ -49,12 +49,20 @@
  *    in high resolution, 1 bpp tiffg4 encoded images in the pdf.
  *
  *      Syntax:
- *       compresspdf basedir scalefactor onebit savecolor quality title fileout
+ *       compresspdf basedir imres scalefactor onebit savecolor
+ *                   quality title fileout
  *
  *    The %basedir is a directory where the input pdf files are located.
  *    The program will operate on every file in this directory with
  *    the ".pdf" extension.
  *
+ *    The %imres is the desired resolution of the rasterization from the
+ *    pdf page to a page image.  Two choices are allowed: 150 and 300 ppi.
+ *    Use 0 for default (150 ppi).  The actual resolution used by the
+ *    renderer depends on the page image size and is computed internally.
+ *    We limit the maximum resolution to 300 ppi because these images are
+ *    RGB uncompressed and are large: 6.3 MB for 150 ppi and 25 MB for 300 ppi.
+ *
  *    The %scalefactor is typically used to downscale the image to
  *    reduce the size of the generated pdf.  It should not affect the
  *    pdf display otherwise.  For normal text on images scanned at 300 ppi,
@@ -122,29 +130,38 @@ l_int32 main(int    argc,
 {
 char       buf[256];
 char      *basedir, *fname, *tail, *basename, *imagedir, *title, *fileout;
-l_int32    render_res, onebit, savecolor, quality, i, n, ret;
+l_int32    imres, render_res, onebit, savecolor, quality, i, n, ret;
 l_float32  scalefactor;
 SARRAY    *sa;
 
-    if (argc != 8)
+    if (argc != 9)
         return ERROR_INT(
-            "Syntax: compresspdf basedir scalefactor onebit savecolor quality "
-            "title fileout", __func__, 1);
+            "Syntax: compresspdf basedir imres scalefactor "
+                     "onebit savecolor quality title fileout", __func__, 1);
     basedir = argv[1];
-    scalefactor = atof(argv[2]);
-    onebit = atoi(argv[3]);  /* set to 1 to enforce 1 bpp tiffg4 encoding */
-    savecolor = atoi(argv[4]);  /* if onebit == 1, set to 1 to save color */
-    quality = atoi(argv[5]);  /* jpeg quality */
-    title = argv[6];
-    fileout = argv[7];
+    imres = atoi(argv[2]);
+    scalefactor = atof(argv[3]);
+    onebit = atoi(argv[4]);  /* set to 1 to enforce 1 bpp tiffg4 encoding */
+    savecolor = atoi(argv[5]);  /* if onebit == 1, set to 1 to save color */
+    quality = atoi(argv[6]);  /* jpeg quality */
+    title = argv[7];
+    fileout = argv[8];
     setLeptDebugOK(1);
+    if (imres == 0) imres = 150;  /* default value */
+    if (imres != 150 && imres != 300) {
+        L_WARNING("imres = %d must be 150 or 300; setting to 150\n",
+                  __func__, imres);
+        imres = 150;
+    }
     if (quality <= 0) quality = 50;  /* default value */
     if (quality < 25) {
-        L_WARNING("quality %d too low; setting to 25\n", __func__, quality);
+        L_WARNING("quality = %d is too low; setting to 25\n",
+                  __func__, quality);
         quality = 25;
     }
     if (quality > 95) {
-        L_WARNING("quality %d too high; setting to 95\n", __func__, quality);
+        L_WARNING("quality = %d is too high; setting to 95\n",
+                  __func__, quality);
         quality = 95;
     }
 
@@ -162,22 +179,24 @@ SARRAY    *sa;
     sarrayWriteStderr(sa);
     n = sarrayGetCount(sa);
 
-        /* Figure out the resolution to use with the image renderer to
-         * generate page images with a resolution of not more than 150 ppi.
-         * These would have a maximum dimension of about 1650 pixels. 
-         * Use the first pdf file in the directory.  */
+        /* Use the first pdf file in the directory to estimate the
+         * resolution to use with the image renderer that will generate
+         * page images with a resolution of either about 150 ppi
+         * (which is the default) or about 300 ppi for special cases.
+         * At 150 and 300 ppi, the page images have maximum dimensions
+         * of about 1650 and 3300 pixels, respectively.  These are the
+         * uncompressed images, written to file, from which the compressed
+         * images will be generated.  */
     fname = sarrayGetString(sa, 0, L_NOCOPY);
     getPdfRendererResolution(fname, imagedir, &render_res);  /* for 300 ppi */
-    render_res /= 2;  /* for 150 ppi */
+    if (imres == 150) render_res /= 2;
 
         /* Rasterize:
-         *     pdftoppm -r 150 fname outroot
+         *     pdftoppm -r 150 fname outroot   [max dimension about 1650 pixels]
+         *     pdftoppm -r 300 fname outroot   [max dimension about 3300 pixels]
          * Use of pdftoppm:
          *    This works on all pdf pages, both wrapped images and pages that
-         *    were made orthographically.  We generate images that are no
-         *    larger than about 1650 pixels in the maximum direction. This
-         *    makes uncompressed 6 MB files and is very fast.  If you want
-         *    higher resolution 1 bpp output, use cleanpdf.c. */
+         *    were made orthographically.  */
     for (i = 0; i < n; i++) {
         fname = sarrayGetString(sa, i, L_NOCOPY);
         splitPathAtDirectory(fname, NULL, &tail);