Port the width/height force feature from jpegtran v8d.

ChangeLog.txt

@@ -33,6 +33,13 @@ the performance of the TurboJPEG Java API.  It can be run with
 [8] cjpeg can now be used to generate JPEG files with the RGB colorspace
 (feature ported from jpeg-8d.)
 
+[9] The width and height in the -crop argument passed to jpegtran can now be
+suffixed with "f" to indicate that, when the upper left corner of the cropping
+region is automatically moved to the nearest iMCU boundary, the bottom right
+corner should be moved by the same amount.  In other words, this feature causes
+jpegtran to strictly honor the specified width/height rather than the specified
+bottom right corner (feature ported from jpeg-8d.)
+
 
 1.2.1
 =====

change.log

@@ -12,6 +12,9 @@ Using this switch suppresses the conversion from RGB
 colorspace input to the default YCbCr JPEG colorspace.
 Thank to Michael Koch for the initial suggestion.
 
+Add option to disable the region adjustment in the transupp crop code.
+Thank to Jeffrey Friedl for the suggestion.
+
 
 Version 8b  16-May-2010
 -----------------------

transupp.c

@@ -2,7 +2,7 @@
  * transupp.c
  *
  * This file was part of the Independent JPEG Group's software:
- * Copyright (C) 1997-2009, Thomas G. Lane, Guido Vollbeding.
+ * Copyright (C) 1997-2011, Thomas G. Lane, Guido Vollbeding.
  * Modifications:
  * Copyright (C) 2010, D. R. Commander.
  * For conditions of distribution and use, see the accompanying README file.
@@ -783,7 +783,7 @@ jt_read_integer (const char ** strptr, JDIMENSION * result)
  * The routine returns TRUE if the spec string is valid, FALSE if not.
  *
  * The crop spec string should have the format
- *	<width>x<height>{+-}<xoffset>{+-}<yoffset>
+ *	<width>[f]x<height>[f]{+-}<xoffset>{+-}<yoffset>
  * where width, height, xoffset, and yoffset are unsigned integers.
  * Each of the elements can be omitted to indicate a default value.
  * (A weakness of this style is that it is not possible to omit xoffset
@@ -805,14 +805,22 @@ jtransform_parse_crop_spec (jpeg_transform_info *info, const char *spec)
     /* fetch width */
     if (! jt_read_integer(&spec, &info->crop_width))
       return FALSE;
-    info->crop_width_set = JCROP_POS;
+    if (*spec == 'f' || *spec == 'F') {
+      spec++;
+      info->crop_width_set = JCROP_FORCE;
+    } else
+      info->crop_width_set = JCROP_POS;
   }
-  if (*spec == 'x' || *spec == 'X') {	
+  if (*spec == 'x' || *spec == 'X') {
     /* fetch height */
     spec++;
     if (! jt_read_integer(&spec, &info->crop_height))
       return FALSE;
-    info->crop_height_set = JCROP_POS;
+    if (*spec == 'f' || *spec == 'F') {
+      spec++;
+      info->crop_height_set = JCROP_FORCE;
+    } else
+      info->crop_height_set = JCROP_POS;
   }
   if (*spec == '+' || *spec == '-') {
     /* fetch xoffset */
@@ -997,10 +1005,16 @@ jtransform_request_workspace (j_decompress_ptr srcinfo,
     else
       yoffset = info->crop_yoffset;
     /* Now adjust so that upper left corner falls at an iMCU boundary */
-    info->output_width =
-      info->crop_width + (xoffset % info->iMCU_sample_width);
-    info->output_height =
-      info->crop_height + (yoffset % info->iMCU_sample_height);
+    if (info->crop_width_set == JCROP_FORCE)
+      info->output_width = info->crop_width;
+    else
+      info->output_width =
+        info->crop_width + (xoffset % info->iMCU_sample_width);
+    if (info->crop_height_set == JCROP_FORCE)
+      info->output_height = info->crop_height;
+    else
+      info->output_height =
+        info->crop_height + (yoffset % info->iMCU_sample_height);
     /* Save x/y offsets measured in iMCUs */
     info->x_crop_offset = xoffset / info->iMCU_sample_width;
     info->y_crop_offset = yoffset / info->iMCU_sample_height;

transupp.h

@@ -1,7 +1,7 @@
 /*
  * transupp.h
  *
- * Copyright (C) 1997-2009, Thomas G. Lane, Guido Vollbeding.
+ * Copyright (C) 1997-2011, Thomas G. Lane, Guido Vollbeding.
  * This file is part of the Independent JPEG Group's software.
  * For conditions of distribution and use, see the accompanying README file.
  *
@@ -57,6 +57,7 @@
  * corner up and/or left to make it so, simultaneously increasing the region
  * dimensions to keep the lower right crop corner unchanged.  (Thus, the
  * output image covers at least the requested region, but may cover more.)
+ * The adjustment of the region dimensions may be optionally disabled.
  *
  * We also provide a lossless-resize option, which is kind of a lossless-crop
  * operation in the DCT coefficient block domain - it discards higher-order
@@ -106,13 +107,15 @@ typedef enum {
 
 /*
  * Codes for crop parameters, which can individually be unspecified,
- * positive, or negative.  (Negative width or height makes no sense, though.)
+ * positive or negative for xoffset or yoffset,
+ * positive or forced for width or height.
  */
 
 typedef enum {
-	JCROP_UNSET,
-	JCROP_POS,
-	JCROP_NEG
+        JCROP_UNSET,
+        JCROP_POS,
+        JCROP_NEG,
+        JCROP_FORCE
 } JCROP_CODE;
 
 /*
@@ -140,9 +143,9 @@ typedef struct {
    * These can be filled in by jtransform_parse_crop_spec().
    */
   JDIMENSION crop_width;	/* Width of selected region */
-  JCROP_CODE crop_width_set;
+  JCROP_CODE crop_width_set;	/* (forced disables adjustment) */
   JDIMENSION crop_height;	/* Height of selected region */
-  JCROP_CODE crop_height_set;
+  JCROP_CODE crop_height_set;	/* (forced disables adjustment) */
   JDIMENSION crop_xoffset;	/* X offset of selected region */
   JCROP_CODE crop_xoffset_set;	/* (negative measures from right edge) */
   JDIMENSION crop_yoffset;	/* Y offset of selected region */