Support additional scaling factors when decompressing

ChangeLog.txt

@@ -1,3 +1,11 @@
+1.3 pre-beta
+============
+
+[1] Added support for additional scaling factors (3/8, 5/8, 3/4, 7/8, 9/8, 5/4,
+11/8, 3/2, 13/8, 7/4, 15/8, and 2) when decompressing.  Currently, the IDCT
+will not be SIMD-accelerated when using any of these scaling factors.
+
+
 1.2.0
 =====
 

Makefile.am

@@ -174,18 +174,38 @@ if WITH_SSE_FLOAT_DCT
 else
 	cmp $(srcdir)/testorig.ppm testoutflt.ppm
 endif
+	./djpeg -dct int -nosmooth -scale 2/1 -ppm -outfile testoutint2_1.ppm $(srcdir)/testorig.jpg
+	cmp $(srcdir)/testimgint2_1.ppm testoutint2_1.ppm
+	./djpeg -dct int -nosmooth -scale 15/8 -ppm -outfile testoutint15_8.ppm $(srcdir)/testorig.jpg
+	cmp $(srcdir)/testimgint15_8.ppm testoutint15_8.ppm
+	./djpeg -dct int -nosmooth -scale 7/4 -ppm -outfile testoutint7_4.ppm $(srcdir)/testorig.jpg
+	cmp $(srcdir)/testimgint7_4.ppm testoutint7_4.ppm
+	./djpeg -dct int -nosmooth -scale 13/8 -ppm -outfile testoutint13_8.ppm $(srcdir)/testorig.jpg
+	cmp $(srcdir)/testimgint13_8.ppm testoutint13_8.ppm
+	./djpeg -dct int -nosmooth -scale 3/2 -ppm -outfile testoutint3_2.ppm $(srcdir)/testorig.jpg
+	cmp $(srcdir)/testimgint3_2.ppm testoutint3_2.ppm
+	./djpeg -dct int -nosmooth -scale 11/8 -ppm -outfile testoutint11_8.ppm $(srcdir)/testorig.jpg
+	cmp $(srcdir)/testimgint11_8.ppm testoutint11_8.ppm
+	./djpeg -dct int -nosmooth -scale 5/4 -ppm -outfile testoutint5_4.ppm $(srcdir)/testorig.jpg
+	cmp $(srcdir)/testimgint5_4.ppm testoutint5_4.ppm
+	./djpeg -dct int -nosmooth -scale 9/8 -ppm -outfile testoutint9_8.ppm $(srcdir)/testorig.jpg
+	cmp $(srcdir)/testimgint9_8.ppm testoutint9_8.ppm
+	./djpeg -dct int -nosmooth -scale 7/8 -ppm -outfile testoutint7_8.ppm $(srcdir)/testorig.jpg
+	cmp $(srcdir)/testimgint7_8.ppm testoutint7_8.ppm
+	./djpeg -dct int -nosmooth -scale 3/4 -ppm -outfile testoutint3_4.ppm $(srcdir)/testorig.jpg
+	cmp $(srcdir)/testimgint3_4.ppm testoutint3_4.ppm
+	./djpeg -dct int -nosmooth -scale 5/8 -ppm -outfile testoutint5_8.ppm $(srcdir)/testorig.jpg
+	cmp $(srcdir)/testimgint5_8.ppm testoutint5_8.ppm
 	./djpeg -dct int -scale 1/2 -ppm -outfile testoutint1_2.ppm $(srcdir)/testorig.jpg
 	cmp $(srcdir)/testimgint1_2.ppm testoutint1_2.ppm
 	./djpeg -dct fast -scale 1/2 -ppm -outfile testoutfst1_2.ppm $(srcdir)/testorig.jpg
 	cmp $(srcdir)/testimgfst1_2.ppm testoutfst1_2.ppm
+	./djpeg -dct int -nosmooth -scale 3/8 -ppm -outfile testoutint3_8.ppm $(srcdir)/testorig.jpg
+	cmp $(srcdir)/testimgint3_8.ppm testoutint3_8.ppm
 	./djpeg -dct int -scale 1/4 -ppm -outfile testoutint1_4.ppm $(srcdir)/testorig.jpg
 	cmp $(srcdir)/testimgint1_4.ppm testoutint1_4.ppm
-	./djpeg -dct fast -scale 1/4 -ppm -outfile testoutfst1_4.ppm $(srcdir)/testorig.jpg
-	cmp $(srcdir)/testimgfst1_4.ppm testoutfst1_4.ppm
 	./djpeg -dct int -scale 1/8 -ppm -outfile testoutint1_8.ppm $(srcdir)/testorig.jpg
 	cmp $(srcdir)/testimgint1_8.ppm testoutint1_8.ppm
-	./djpeg -dct fast -scale 1/8 -ppm -outfile testoutfst1_8.ppm $(srcdir)/testorig.jpg
-	cmp $(srcdir)/testimgfst1_8.ppm testoutfst1_8.ppm
 	./djpeg -dct int -bmp -colors 256 -outfile testout.bmp  $(srcdir)/testorig.jpg
 	cmp $(srcdir)/testimg.bmp testout.bmp
 if WITH_ARITH_ENC

djpeg.1

@@ -1,4 +1,4 @@
-.TH DJPEG 1 "11 October 2010"
+.TH DJPEG 1 "27 January 2012"
 .SH NAME
 djpeg \- decompress a JPEG file to an image file
 .SH SYNOPSIS
@@ -62,8 +62,9 @@ runs noticeably faster in this mode.
 .TP
 .BI \-scale " M/N"
 Scale the output image by a factor M/N.  Currently the scale factor must be
-1/1, 1/2, 1/4, or 1/8.  Scaling is handy if the image is larger than your
-screen; also,
+M/8, where M is an integer between 1 and 16 inclusive, or any reduced fraction
+thereof (such as 1/2, 3/4, etc.)  Scaling is handy if the image is larger than
+your screen; also,
 .B djpeg
 runs much faster when scaling down the output.
 .TP

jdct.h

@@ -95,9 +95,21 @@ typedef FAST_FLOAT FLOAT_MULT_TYPE; /* preferred floating type */
 #define jpeg_idct_islow		jRDislow
 #define jpeg_idct_ifast		jRDifast
 #define jpeg_idct_float		jRDfloat
+#define jpeg_idct_7x7		jRD7x7
+#define jpeg_idct_6x6		jRD6x6
+#define jpeg_idct_5x5		jRD5x5
 #define jpeg_idct_4x4		jRD4x4
+#define jpeg_idct_3x3		jRD3x3
 #define jpeg_idct_2x2		jRD2x2
 #define jpeg_idct_1x1		jRD1x1
+#define jpeg_idct_9x9		jRD9x9
+#define jpeg_idct_10x10		jRD10x10
+#define jpeg_idct_11x11		jRD11x11
+#define jpeg_idct_12x12		jRD12x12
+#define jpeg_idct_13x13		jRD13x13
+#define jpeg_idct_14x14		jRD14x14
+#define jpeg_idct_15x15		jRD15x15
+#define jpeg_idct_16x16		jRD16x16
 #endif /* NEED_SHORT_EXTERNAL_NAMES */
 
 /* Extern declarations for the forward and inverse DCT routines. */
@@ -115,15 +127,51 @@ EXTERN(void) jpeg_idct_ifast
 EXTERN(void) jpeg_idct_float
     JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
 	 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
+EXTERN(void) jpeg_idct_7x7
+    JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
+	 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
+EXTERN(void) jpeg_idct_6x6
+    JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
+	 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
+EXTERN(void) jpeg_idct_5x5
+    JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
+	 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
 EXTERN(void) jpeg_idct_4x4
     JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
 	 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
+EXTERN(void) jpeg_idct_3x3
+    JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
+	 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
 EXTERN(void) jpeg_idct_2x2
     JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
 	 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
 EXTERN(void) jpeg_idct_1x1
     JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
 	 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
+EXTERN(void) jpeg_idct_9x9
+    JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
+	 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
+EXTERN(void) jpeg_idct_10x10
+    JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
+	 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
+EXTERN(void) jpeg_idct_11x11
+    JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
+	 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
+EXTERN(void) jpeg_idct_12x12
+    JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
+	 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
+EXTERN(void) jpeg_idct_13x13
+    JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
+	 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
+EXTERN(void) jpeg_idct_14x14
+    JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
+	 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
+EXTERN(void) jpeg_idct_15x15
+    JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
+	 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
+EXTERN(void) jpeg_idct_16x16
+    JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
+	 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
 
 
 /*

jddctmgr.c

@@ -2,6 +2,7 @@
  * jddctmgr.c
  *
  * Copyright (C) 1994-1996, Thomas G. Lane.
+ * Modified 2002-2010 by Guido Vollbeding.
  * Copyright 2009 Pierre Ossman <ossman@cendio.se> for Cendio AB
  * Copyright (C) 2010, D. R. Commander.
  * This file is part of the Independent JPEG Group's software.
@@ -115,6 +116,10 @@ start_pass (j_decompress_ptr cinfo)
         method_ptr = jpeg_idct_2x2;
       method = JDCT_ISLOW;	/* jidctred uses islow-style table */
       break;
+    case 3:
+      method_ptr = jpeg_idct_3x3;
+      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
+      break;
     case 4:
       if (jsimd_can_idct_4x4())
         method_ptr = jsimd_idct_4x4;
@@ -122,6 +127,18 @@ start_pass (j_decompress_ptr cinfo)
         method_ptr = jpeg_idct_4x4;
       method = JDCT_ISLOW;	/* jidctred uses islow-style table */
       break;
+    case 5:
+      method_ptr = jpeg_idct_5x5;
+      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
+      break;
+    case 6:
+      method_ptr = jpeg_idct_6x6;
+      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
+      break;
+    case 7:
+      method_ptr = jpeg_idct_7x7;
+      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
+      break;
 #endif
     case DCTSIZE:
       switch (cinfo->dct_method) {
@@ -157,6 +174,38 @@ start_pass (j_decompress_ptr cinfo)
 	break;
       }
       break;
+    case 9:
+      method_ptr = jpeg_idct_9x9;
+      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
+      break;
+    case 10:
+      method_ptr = jpeg_idct_10x10;
+      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
+      break;
+    case 11:
+      method_ptr = jpeg_idct_11x11;
+      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
+      break;
+    case 12:
+      method_ptr = jpeg_idct_12x12;
+      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
+      break;
+    case 13:
+      method_ptr = jpeg_idct_13x13;
+      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
+      break;
+    case 14:
+      method_ptr = jpeg_idct_14x14;
+      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
+      break;
+    case 15:
+      method_ptr = jpeg_idct_15x15;
+      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
+      break;
+    case 16:
+      method_ptr = jpeg_idct_16x16;
+      method = JDCT_ISLOW;	/* jidctint uses islow-style table */
+      break;
     default:
       ERREXIT1(cinfo, JERR_BAD_DCTSIZE, compptr->_DCT_scaled_size);
       break;

jdinput.c

@@ -2,7 +2,6 @@
  * jdinput.c
  *
  * Copyright (C) 1991-1997, Thomas G. Lane.
- * Modified 2002-2009 by Guido Vollbeding.
  * Copyright (C) 2010, D. R. Commander.
  * This file is part of the Independent JPEG Group's software.
  * For conditions of distribution and use, see the accompanying README file.
@@ -38,79 +37,6 @@ METHODDEF(int) consume_markers JPP((j_decompress_ptr cinfo));
  * Routines to calculate various quantities related to the size of the image.
  */
 
-
-#if JPEG_LIB_VERSION >= 80
-/*
- * Compute output image dimensions and related values.
- * NOTE: this is exported for possible use by application.
- * Hence it mustn't do anything that can't be done twice.
- */
-
-GLOBAL(void)
-jpeg_core_output_dimensions (j_decompress_ptr cinfo)
-/* Do computations that are needed before master selection phase.
- * This function is used for transcoding and full decompression.
- */
-{
-#ifdef IDCT_SCALING_SUPPORTED
-  int ci;
-  jpeg_component_info *compptr;
-
-  /* Compute actual output image dimensions and DCT scaling choices. */
-  if (cinfo->scale_num * cinfo->block_size <= cinfo->scale_denom) {
-    /* Provide 1/block_size scaling */
-    cinfo->output_width = (JDIMENSION)
-      jdiv_round_up((long) cinfo->image_width, (long) cinfo->block_size);
-    cinfo->output_height = (JDIMENSION)
-      jdiv_round_up((long) cinfo->image_height, (long) cinfo->block_size);
-    cinfo->min_DCT_h_scaled_size = 1;
-    cinfo->min_DCT_v_scaled_size = 1;
-  } else if (cinfo->scale_num * cinfo->block_size <= cinfo->scale_denom * 2) {
-    /* Provide 2/block_size scaling */
-    cinfo->output_width = (JDIMENSION)
-      jdiv_round_up((long) cinfo->image_width * 2L, (long) cinfo->block_size);
-    cinfo->output_height = (JDIMENSION)
-      jdiv_round_up((long) cinfo->image_height * 2L, (long) cinfo->block_size);
-    cinfo->min_DCT_h_scaled_size = 2;
-    cinfo->min_DCT_v_scaled_size = 2;
-  } else if (cinfo->scale_num * cinfo->block_size <= cinfo->scale_denom * 4) {
-    /* Provide 4/block_size scaling */
-    cinfo->output_width = (JDIMENSION)
-      jdiv_round_up((long) cinfo->image_width * 4L, (long) cinfo->block_size);
-    cinfo->output_height = (JDIMENSION)
-      jdiv_round_up((long) cinfo->image_height * 4L, (long) cinfo->block_size);
-    cinfo->min_DCT_h_scaled_size = 4;
-    cinfo->min_DCT_v_scaled_size = 4;
-  } else if (cinfo->scale_num * cinfo->block_size <= cinfo->scale_denom * 8) {
-    /* Provide 8/block_size scaling */
-    cinfo->output_width = (JDIMENSION)
-      jdiv_round_up((long) cinfo->image_width * 8L, (long) cinfo->block_size);
-    cinfo->output_height = (JDIMENSION)
-      jdiv_round_up((long) cinfo->image_height * 8L, (long) cinfo->block_size);
-    cinfo->min_DCT_h_scaled_size = 8;
-    cinfo->min_DCT_v_scaled_size = 8;
-  }
-  /* Recompute dimensions of components */
-  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
-       ci++, compptr++) {
-    compptr->DCT_h_scaled_size = cinfo->min_DCT_h_scaled_size;
-    compptr->DCT_v_scaled_size = cinfo->min_DCT_v_scaled_size;
-  }
-
-#else /* !IDCT_SCALING_SUPPORTED */
-
-  /* Hardwire it to "no scaling" */
-  cinfo->output_width = cinfo->image_width;
-  cinfo->output_height = cinfo->image_height;
-  /* jdinput.c has already initialized DCT_scaled_size,
-   * and has computed unscaled downsampled_width and downsampled_height.
-   */
-
-#endif /* IDCT_SCALING_SUPPORTED */
-}
-#endif
-
-
 LOCAL(void)
 initial_setup (j_decompress_ptr cinfo)
 /* Called once, when first SOS marker is reached */

jdmaster.c

@@ -2,6 +2,7 @@
  * jdmaster.c
  *
  * Copyright (C) 1991-1997, Thomas G. Lane.
+ * Modified 2002-2009 by Guido Vollbeding.
  * Copyright (C) 2009-2011, D. R. Commander.
  * This file is part of the Independent JPEG Group's software.
  * For conditions of distribution and use, see the accompanying README file.
@@ -85,6 +86,177 @@ use_merged_upsample (j_decompress_ptr cinfo)
 }
 
 
+/*
+ * Compute output image dimensions and related values.
+ * NOTE: this is exported for possible use by application.
+ * Hence it mustn't do anything that can't be done twice.
+ */
+
+#if JPEG_LIB_VERSION >= 80
+GLOBAL(void)
+#else
+LOCAL(void)
+#endif
+jpeg_core_output_dimensions (j_decompress_ptr cinfo)
+/* Do computations that are needed before master selection phase.
+ * This function is used for transcoding and full decompression.
+ */
+{
+#ifdef IDCT_SCALING_SUPPORTED
+  int ci;
+  jpeg_component_info *compptr;
+
+  /* Compute actual output image dimensions and DCT scaling choices. */
+  if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom) {
+    /* Provide 1/block_size scaling */
+    cinfo->output_width = (JDIMENSION)
+      jdiv_round_up((long) cinfo->image_width, (long) DCTSIZE);
+    cinfo->output_height = (JDIMENSION)
+      jdiv_round_up((long) cinfo->image_height, (long) DCTSIZE);
+    cinfo->_min_DCT_h_scaled_size = 1;
+    cinfo->_min_DCT_v_scaled_size = 1;
+  } else if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom * 2) {
+    /* Provide 2/block_size scaling */
+    cinfo->output_width = (JDIMENSION)
+      jdiv_round_up((long) cinfo->image_width * 2L, (long) DCTSIZE);
+    cinfo->output_height = (JDIMENSION)
+      jdiv_round_up((long) cinfo->image_height * 2L, (long) DCTSIZE);
+    cinfo->_min_DCT_h_scaled_size = 2;
+    cinfo->_min_DCT_v_scaled_size = 2;
+  } else if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom * 3) {
+    /* Provide 3/block_size scaling */
+    cinfo->output_width = (JDIMENSION)
+      jdiv_round_up((long) cinfo->image_width * 3L, (long) DCTSIZE);
+    cinfo->output_height = (JDIMENSION)
+      jdiv_round_up((long) cinfo->image_height * 3L, (long) DCTSIZE);
+    cinfo->_min_DCT_h_scaled_size = 3;
+    cinfo->_min_DCT_v_scaled_size = 3;
+  } else if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom * 4) {
+    /* Provide 4/block_size scaling */
+    cinfo->output_width = (JDIMENSION)
+      jdiv_round_up((long) cinfo->image_width * 4L, (long) DCTSIZE);
+    cinfo->output_height = (JDIMENSION)
+      jdiv_round_up((long) cinfo->image_height * 4L, (long) DCTSIZE);
+    cinfo->_min_DCT_h_scaled_size = 4;
+    cinfo->_min_DCT_v_scaled_size = 4;
+  } else if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom * 5) {
+    /* Provide 5/block_size scaling */
+    cinfo->output_width = (JDIMENSION)
+      jdiv_round_up((long) cinfo->image_width * 5L, (long) DCTSIZE);
+    cinfo->output_height = (JDIMENSION)
+      jdiv_round_up((long) cinfo->image_height * 5L, (long) DCTSIZE);
+    cinfo->_min_DCT_h_scaled_size = 5;
+    cinfo->_min_DCT_v_scaled_size = 5;
+  } else if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom * 6) {
+    /* Provide 6/block_size scaling */
+    cinfo->output_width = (JDIMENSION)
+      jdiv_round_up((long) cinfo->image_width * 6L, (long) DCTSIZE);
+    cinfo->output_height = (JDIMENSION)
+      jdiv_round_up((long) cinfo->image_height * 6L, (long) DCTSIZE);
+    cinfo->_min_DCT_h_scaled_size = 6;
+    cinfo->_min_DCT_v_scaled_size = 6;
+  } else if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom * 7) {
+    /* Provide 7/block_size scaling */
+    cinfo->output_width = (JDIMENSION)
+      jdiv_round_up((long) cinfo->image_width * 7L, (long) DCTSIZE);
+    cinfo->output_height = (JDIMENSION)
+      jdiv_round_up((long) cinfo->image_height * 7L, (long) DCTSIZE);
+    cinfo->_min_DCT_h_scaled_size = 7;
+    cinfo->_min_DCT_v_scaled_size = 7;
+  } else if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom * 8) {
+    /* Provide 8/block_size scaling */
+    cinfo->output_width = (JDIMENSION)
+      jdiv_round_up((long) cinfo->image_width * 8L, (long) DCTSIZE);
+    cinfo->output_height = (JDIMENSION)
+      jdiv_round_up((long) cinfo->image_height * 8L, (long) DCTSIZE);
+    cinfo->_min_DCT_h_scaled_size = 8;
+    cinfo->_min_DCT_v_scaled_size = 8;
+  } else if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom * 9) {
+    /* Provide 9/block_size scaling */
+    cinfo->output_width = (JDIMENSION)
+      jdiv_round_up((long) cinfo->image_width * 9L, (long) DCTSIZE);
+    cinfo->output_height = (JDIMENSION)
+      jdiv_round_up((long) cinfo->image_height * 9L, (long) DCTSIZE);
+    cinfo->_min_DCT_h_scaled_size = 9;
+    cinfo->_min_DCT_v_scaled_size = 9;
+  } else if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom * 10) {
+    /* Provide 10/block_size scaling */
+    cinfo->output_width = (JDIMENSION)
+      jdiv_round_up((long) cinfo->image_width * 10L, (long) DCTSIZE);
+    cinfo->output_height = (JDIMENSION)
+      jdiv_round_up((long) cinfo->image_height * 10L, (long) DCTSIZE);
+    cinfo->_min_DCT_h_scaled_size = 10;
+    cinfo->_min_DCT_v_scaled_size = 10;
+  } else if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom * 11) {
+    /* Provide 11/block_size scaling */
+    cinfo->output_width = (JDIMENSION)
+      jdiv_round_up((long) cinfo->image_width * 11L, (long) DCTSIZE);
+    cinfo->output_height = (JDIMENSION)
+      jdiv_round_up((long) cinfo->image_height * 11L, (long) DCTSIZE);
+    cinfo->_min_DCT_h_scaled_size = 11;
+    cinfo->_min_DCT_v_scaled_size = 11;
+  } else if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom * 12) {
+    /* Provide 12/block_size scaling */
+    cinfo->output_width = (JDIMENSION)
+      jdiv_round_up((long) cinfo->image_width * 12L, (long) DCTSIZE);
+    cinfo->output_height = (JDIMENSION)
+      jdiv_round_up((long) cinfo->image_height * 12L, (long) DCTSIZE);
+    cinfo->_min_DCT_h_scaled_size = 12;
+    cinfo->_min_DCT_v_scaled_size = 12;
+  } else if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom * 13) {
+    /* Provide 13/block_size scaling */
+    cinfo->output_width = (JDIMENSION)
+      jdiv_round_up((long) cinfo->image_width * 13L, (long) DCTSIZE);
+    cinfo->output_height = (JDIMENSION)
+      jdiv_round_up((long) cinfo->image_height * 13L, (long) DCTSIZE);
+    cinfo->_min_DCT_h_scaled_size = 13;
+    cinfo->_min_DCT_v_scaled_size = 13;
+  } else if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom * 14) {
+    /* Provide 14/block_size scaling */
+    cinfo->output_width = (JDIMENSION)
+      jdiv_round_up((long) cinfo->image_width * 14L, (long) DCTSIZE);
+    cinfo->output_height = (JDIMENSION)
+      jdiv_round_up((long) cinfo->image_height * 14L, (long) DCTSIZE);
+    cinfo->_min_DCT_h_scaled_size = 14;
+    cinfo->_min_DCT_v_scaled_size = 14;
+  } else if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom * 15) {
+    /* Provide 15/block_size scaling */
+    cinfo->output_width = (JDIMENSION)
+      jdiv_round_up((long) cinfo->image_width * 15L, (long) DCTSIZE);
+    cinfo->output_height = (JDIMENSION)
+      jdiv_round_up((long) cinfo->image_height * 15L, (long) DCTSIZE);
+    cinfo->_min_DCT_h_scaled_size = 15;
+    cinfo->_min_DCT_v_scaled_size = 15;
+  } else {
+    /* Provide 16/block_size scaling */
+    cinfo->output_width = (JDIMENSION)
+      jdiv_round_up((long) cinfo->image_width * 16L, (long) DCTSIZE);
+    cinfo->output_height = (JDIMENSION)
+      jdiv_round_up((long) cinfo->image_height * 16L, (long) DCTSIZE);
+    cinfo->_min_DCT_h_scaled_size = 16;
+    cinfo->_min_DCT_v_scaled_size = 16;
+  }
+
+  /* Recompute dimensions of components */
+  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
+       ci++, compptr++) {
+    compptr->_DCT_h_scaled_size = cinfo->_min_DCT_h_scaled_size;
+    compptr->_DCT_v_scaled_size = cinfo->_min_DCT_v_scaled_size;
+  }
+
+#else /* !IDCT_SCALING_SUPPORTED */
+
+  /* Hardwire it to "no scaling" */
+  cinfo->output_width = cinfo->image_width;
+  cinfo->output_height = cinfo->image_height;
+  /* jdinput.c has already initialized DCT_scaled_size,
+   * and has computed unscaled downsampled_width and downsampled_height.
+   */
+
+#endif /* IDCT_SCALING_SUPPORTED */
+}
+
+
 /*
  * Compute output image dimensions and related values.
  * NOTE: this is exported for possible use by application.
@@ -105,52 +277,11 @@ jpeg_calc_output_dimensions (j_decompress_ptr cinfo)
   if (cinfo->global_state != DSTATE_READY)
     ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
 
+  /* Compute core output image dimensions and DCT scaling choices. */
+  jpeg_core_output_dimensions(cinfo);
+
 #ifdef IDCT_SCALING_SUPPORTED
 
-  /* Compute actual output image dimensions and DCT scaling choices. */
-  if (cinfo->scale_num * 8 <= cinfo->scale_denom) {
-    /* Provide 1/8 scaling */
-    cinfo->output_width = (JDIMENSION)
-      jdiv_round_up((long) cinfo->image_width, 8L);
-    cinfo->output_height = (JDIMENSION)
-      jdiv_round_up((long) cinfo->image_height, 8L);
-#if JPEG_LIB_VERSION >= 70
-    cinfo->min_DCT_h_scaled_size = cinfo->min_DCT_v_scaled_size = 1;
-#else
-    cinfo->min_DCT_scaled_size = 1;
-#endif
-  } else if (cinfo->scale_num * 4 <= cinfo->scale_denom) {
-    /* Provide 1/4 scaling */
-    cinfo->output_width = (JDIMENSION)
-      jdiv_round_up((long) cinfo->image_width, 4L);
-    cinfo->output_height = (JDIMENSION)
-      jdiv_round_up((long) cinfo->image_height, 4L);
-#if JPEG_LIB_VERSION >= 70
-    cinfo->min_DCT_h_scaled_size = cinfo->min_DCT_v_scaled_size = 2;
-#else
-    cinfo->min_DCT_scaled_size = 2;
-#endif
-  } else if (cinfo->scale_num * 2 <= cinfo->scale_denom) {
-    /* Provide 1/2 scaling */
-    cinfo->output_width = (JDIMENSION)
-      jdiv_round_up((long) cinfo->image_width, 2L);
-    cinfo->output_height = (JDIMENSION)
-      jdiv_round_up((long) cinfo->image_height, 2L);
-#if JPEG_LIB_VERSION >= 70
-    cinfo->min_DCT_h_scaled_size = cinfo->min_DCT_v_scaled_size = 4;
-#else
-    cinfo->min_DCT_scaled_size = 4;
-#endif
-  } else {
-    /* Provide 1/1 scaling */
-    cinfo->output_width = cinfo->image_width;
-    cinfo->output_height = cinfo->image_height;
-#if JPEG_LIB_VERSION >= 70
-    cinfo->min_DCT_h_scaled_size = cinfo->min_DCT_v_scaled_size = DCTSIZE;
-#else
-    cinfo->min_DCT_scaled_size = DCTSIZE;
-#endif
-  }
   /* In selecting the actual DCT scaling for each component, we try to
    * scale up the chroma components via IDCT scaling rather than upsampling.
    * This saves time if the upsampler gets to use 1:1 scaling.

jpegcomp.h

@@ -11,6 +11,8 @@
 
 #if JPEG_LIB_VERSION >= 70
 #define _DCT_scaled_size DCT_h_scaled_size
+#define _DCT_h_scaled_size DCT_h_scaled_size
+#define _DCT_v_scaled_size DCT_v_scaled_size
 #define _min_DCT_scaled_size min_DCT_h_scaled_size
 #define _min_DCT_h_scaled_size min_DCT_h_scaled_size
 #define _min_DCT_v_scaled_size min_DCT_v_scaled_size
@@ -18,6 +20,8 @@
 #define _jpeg_height jpeg_height
 #else
 #define _DCT_scaled_size DCT_scaled_size
+#define _DCT_h_scaled_size DCT_scaled_size
+#define _DCT_v_scaled_size DCT_scaled_size
 #define _min_DCT_scaled_size min_DCT_scaled_size
 #define _min_DCT_h_scaled_size min_DCT_scaled_size
 #define _min_DCT_v_scaled_size min_DCT_scaled_size

libjpeg.txt

@@ -1113,7 +1113,8 @@ J_COLOR_SPACE out_color_space
 unsigned int scale_num, scale_denom
 	Scale the image by the fraction scale_num/scale_denom.  Default is
 	1/1, or no scaling.  Currently, the only supported scaling ratios
-	are 1/1, 1/2, 1/4, and 1/8.  (The library design allows for arbitrary
+	are M/8 with all M from 1 to 16, or any reduced fraction thereof (such
+	as 1/2, 3/4, etc.)  (The library design allows for arbitrary
 	scaling ratios but this is not likely to be implemented any time soon.)
 	Smaller scaling ratios permit significantly faster decoding since
 	fewer pixels need be processed and a simpler IDCT method can be used.

testimgfst1_8.ppm

@@ -1,4 +0,0 @@
-P6
-29 19
-255
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