Add jpeg restart_interval option. (libvips#2468)

manthey · web-flow · commit 46a67cfab963 · 2021-10-08T17:33:32.000+01:00
* Add jpeg restart_interval option.

This allows saving a jpeg with MCU restarts.

* Fix code style.  Add description of restart_interval.

* Add a basic test based on output length.

* Update main change log.
diff --git a/ChangeLog b/ChangeLog
@@ -11,6 +11,7 @@
 - don't use atexit for cleanup, it's too unreliable
 - tiff writer loops for the whole image rather than per page [LionelArn2]
 - fix VipsSource with named pipes [vibbix]
+- added restart_interval option to jpegsave [manthey]
 
 16/8/21 started 8.11.4
 - fix off-by-one error in new rank fast path
diff --git a/libvips/foreign/jpegsave.c b/libvips/foreign/jpegsave.c
@@ -103,6 +103,10 @@ typedef struct _VipsForeignSaveJpeg {
 	 */
 	int quant_table;
 
+	/* Use an MCU restart interval.
+	 */
+	int restart_interval;
+
 } VipsForeignSaveJpeg;
 
 typedef VipsForeignSaveClass VipsForeignSaveJpegClass;
@@ -231,6 +235,14 @@ vips_foreign_save_jpeg_class_init( VipsForeignSaveJpegClass *class )
 		G_STRUCT_OFFSET( VipsForeignSaveJpeg, subsample_mode ),
 		VIPS_TYPE_FOREIGN_SUBSAMPLE,
 		VIPS_FOREIGN_SUBSAMPLE_AUTO );
+
+	VIPS_ARG_INT( class, "restart_interval", 20,
+		_( "Restart interval" ),
+		_( "Add restart markers every specified number of mcu" ),
+		VIPS_ARGUMENT_OPTIONAL_INPUT,
+		G_STRUCT_OFFSET( VipsForeignSaveJpeg, restart_interval ),
+		0, INT_MAX, 0 );
+
 }
 
 static void
@@ -268,7 +280,8 @@ vips_foreign_save_jpeg_target_build( VipsObject *object )
 		jpeg->Q, jpeg->profile, jpeg->optimize_coding, 
 		jpeg->interlace, save->strip, jpeg->trellis_quant,
 		jpeg->overshoot_deringing, jpeg->optimize_scans,
-		jpeg->quant_table, jpeg->subsample_mode ) )
+		jpeg->quant_table, jpeg->subsample_mode,
+		jpeg->restart_interval ) )
 		return( -1 );
 
 	return( 0 );
@@ -334,7 +347,8 @@ vips_foreign_save_jpeg_file_build( VipsObject *object )
 		jpeg->Q, jpeg->profile, jpeg->optimize_coding, 
 		jpeg->interlace, save->strip, jpeg->trellis_quant,
 		jpeg->overshoot_deringing, jpeg->optimize_scans,
-		jpeg->quant_table, jpeg->subsample_mode ) ) {
+		jpeg->quant_table, jpeg->subsample_mode,
+		jpeg->restart_interval ) ) {
 		VIPS_UNREF( target );
 		return( -1 );
 	}
@@ -404,7 +418,8 @@ vips_foreign_save_jpeg_buffer_build( VipsObject *object )
 		jpeg->Q, jpeg->profile, jpeg->optimize_coding, 
 		jpeg->interlace, save->strip, jpeg->trellis_quant,
 		jpeg->overshoot_deringing, jpeg->optimize_scans,
-		jpeg->quant_table, jpeg->subsample_mode ) ) {
+		jpeg->quant_table, jpeg->subsample_mode,
+		jpeg->restart_interval ) ) {
 		VIPS_UNREF( target );
 		return( -1 );
 	}
@@ -477,7 +492,8 @@ vips_foreign_save_jpeg_mime_build( VipsObject *object )
 		jpeg->Q, jpeg->profile, jpeg->optimize_coding, 
 		jpeg->interlace, save->strip, jpeg->trellis_quant,
 		jpeg->overshoot_deringing, jpeg->optimize_scans,
-		jpeg->quant_table, jpeg->subsample_mode ) ) {
+		jpeg->quant_table, jpeg->subsample_mode,
+		jpeg->restart_interval ) ) {
 		VIPS_UNREF( target );
 		return( -1 );
 	}
@@ -534,6 +550,7 @@ vips_foreign_save_jpeg_mime_init( VipsForeignSaveJpegMime *mime )
  * * @overshoot_deringing: %gboolean, overshoot samples with extreme values
  * * @optimize_scans: %gboolean, split DCT coefficients into separate scans
  * * @quant_table: %gint, quantization table index
+ * * @restart_interval: %gint, restart interval in mcu
  *
  * Write a VIPS image to a file as JPEG.
  *
@@ -604,6 +621,12 @@ vips_foreign_save_jpeg_mime_init( VipsForeignSaveJpegMime *mime )
  * For maximum compression with mozjpeg, a useful set of options is `strip, 
  * optimize-coding, interlace, optimize-scans, trellis-quant, quant_table=3`.
  *
+ * By default, the output stream won't have restart markers.  If a non-zero
+ * restart_interval is specified, a restart marker will be added after each
+ * specified number of MCU blocks.  This makes the stream more recoverable
+ * if there are transmission errors, but also allows for some decoders to read
+ * part of the JPEG without decoding the whole stream.
+ *
  * The image is automatically converted to RGB, Monochrome or CMYK before 
  * saving. 
  *
@@ -650,6 +673,7 @@ vips_jpegsave( VipsImage *in, const char *filename, ... )
  * * @overshoot_deringing: %gboolean, overshoot samples with extreme values
  * * @optimize_scans: %gboolean, split DCT coefficients into separate scans
  * * @quant_table: %gint, quantization table index
+ * * @restart_interval: %gint, restart interval in mcu
  *
  * As vips_jpegsave(), but save to a target.
  *
@@ -689,6 +713,7 @@ vips_jpegsave_target( VipsImage *in, VipsTarget *target, ... )
  * * @overshoot_deringing: %gboolean, overshoot samples with extreme values
  * * @optimize_scans: %gboolean, split DCT coefficients into separate scans
  * * @quant_table: %gint, quantization table index
+ * * @restart_interval: %gint, restart interval in mcu
  *
  * As vips_jpegsave(), but save to a memory buffer. 
  *
@@ -745,6 +770,7 @@ vips_jpegsave_buffer( VipsImage *in, void **buf, size_t *len, ... )
  * * @overshoot_deringing: %gboolean, overshoot samples with extreme values
  * * @optimize_scans: %gboolean, split DCT coefficients into separate scans
  * * @quant_table: %gint, quantization table index
+ * * @restart_interval: %gint, restart interval in mcu
  *
  * As vips_jpegsave(), but save as a mime jpeg on stdout.
  *
diff --git a/libvips/foreign/pforeign.h b/libvips/foreign/pforeign.h
@@ -174,7 +174,7 @@ int vips__jpeg_write_target( VipsImage *in, VipsTarget *target,
 	gboolean optimize_coding, gboolean progressive, gboolean strip,
 	gboolean trellis_quant, gboolean overshoot_deringing,
 	gboolean optimize_scans, int quant_table,
-	VipsForeignSubsample subsample_mode );
+	VipsForeignSubsample subsample_mode, int restart_interval );
 
 int vips__jpeg_read_source( VipsSource *source, VipsImage *out,
 	gboolean header_only, int shrink, int fail, gboolean autorotate );
@@ -252,5 +252,3 @@ extern const char *vips__jxl_suffs[];
 #endif /*__cplusplus*/
 
 #endif /*VIPS_PFOREIGN_H*/
-
-
diff --git a/libvips/foreign/vips2jpeg.c b/libvips/foreign/vips2jpeg.c
@@ -96,6 +96,8 @@
  * 	- add subsample_mode, deprecate no_subsample
  * 13/9/20
  * 	- only write JFIF resolution if we don't have EXIF
+ * 7/10/21 Manthey
+ *  - add restart_interval
  */
 
 /*
@@ -540,7 +542,7 @@ write_vips( Write *write, int qfac, const char *profile,
 	gboolean optimize_coding, gboolean progressive, gboolean strip, 
 	gboolean trellis_quant, gboolean overshoot_deringing,
 	gboolean optimize_scans, int quant_table,
-	VipsForeignSubsample subsample_mode )
+	VipsForeignSubsample subsample_mode, int restart_interval )
 {
 	VipsImage *in;
 	J_COLOR_SPACE space;
@@ -607,6 +609,10 @@ write_vips( Write *write, int qfac, const char *profile,
 	 */
 	write->cinfo.optimize_coding = optimize_coding;
 
+	/* Use a restart interval.
+	 */
+	if( restart_interval > 0 )
+		write->cinfo.restart_interval = restart_interval;
 #ifdef HAVE_JPEG_EXT_PARAMS
 	/* Apply trellis quantisation to each 8x8 block. Implies 
 	 * "optimize_coding".
@@ -846,7 +852,8 @@ vips__jpeg_write_target( VipsImage *in, VipsTarget *target,
 	gboolean optimize_coding, gboolean progressive,
 	gboolean strip, gboolean trellis_quant,
 	gboolean overshoot_deringing, gboolean optimize_scans,
-	int quant_table, VipsForeignSubsample subsample_mode)
+	int quant_table, VipsForeignSubsample subsample_mode,
+	int restart_interval)
 {
 	Write *write;
 
@@ -873,7 +880,7 @@ vips__jpeg_write_target( VipsImage *in, VipsTarget *target,
 	if( write_vips( write, 
 		Q, profile, optimize_coding, progressive, strip,
 		trellis_quant, overshoot_deringing, optimize_scans, 
-		quant_table, subsample_mode ) ) {
+		quant_table, subsample_mode, restart_interval ) ) {
 		write_destroy( write );
 		return( -1 );
 	}
diff --git a/test/test-suite/test_foreign.py b/test/test-suite/test_foreign.py
@@ -294,6 +294,15 @@ def test_jpegsave(self):
         assert len(q90_subsample_on) < len(q90) 
         assert len(q90_subsample_off) == len(q90_subsample_auto)
 
+        # A non-zero restart_interval should result in a bigger file.
+        # Otherwise, smaller restart intervals will have more restart markers
+        # and therefore be larger
+        r0 = im.jpegsave_buffer(restart_interval=0)
+        r10 = im.jpegsave_buffer(restart_interval=10)
+        r2 = im.jpegsave_buffer(restart_interval=2)
+        assert len(r10) > len(r0)
+        assert len(r2) > len(r10)
+
     @skip_if_no("jpegload")
     def test_truncated(self):
         # This should open (there's enough there for the header)
