add "no-subsample" option to jpeg save

turns off chroma subsampling

TODO

@@ -1,28 +1,6 @@
-- large alpha PNGs seem to need huge amounts of ram to process
-
-john@bambam ~/pics $ vipsthumbnail wtc.png
-memory: high-water mark 31.37 MB
-john@bambam ~/pics $ vipsthumbnail wtc.png --linear
-memory: high-water mark 47.83 MB
-
-john@bambam ~/pics $ vipsthumbnail wtc_alpha.png 
-memory: high-water mark 41.85 MB
-john@bambam ~/pics $ vipsthumbnail wtc_alpha.png --linear
-memory: high-water mark 101.59 MB
-john@bambam ~/pics $ 
-
-  it seems to be the vips_colourspace() cast from sRGB to XYZ that's doing it?
-  how odd
-
-  maybe the thing that detaches and reattaches the alpha?
-
-- still don't get progress feedback in nip2 for a long png save, eg. make a
-  4-band wtc, save as png
 
 - support --strip for other writers
 
-- vipstumbnail is broken for the gamma trick png on eric brasseur's page
-
 - vipsthumbnail could shrink-on-load openslide and pyr tiff as well?
 
 - look again at gcc auto-vectorisation, what would we need to do to use this?

libvips/foreign/foreign.c

@@ -1389,7 +1389,7 @@ vips_foreign_save_class_init( VipsForeignSaveClass *class )
 
 	/* I think all savers are sequential. Hopefully.
 	 */
-	operation_class->flags |= VIPS_OPERATION_SEQUENTIAL;
+	operation_class->flags |= VIPS_OPERATION_SEQUENTIAL_UNBUFFERED;
 
 	/* Must not cache savers.
 	 */

libvips/foreign/jpegsave.c

@@ -87,6 +87,10 @@ typedef struct _VipsForeignSaveJpeg {
 	 */
 	gboolean interlace;
 
+	/* Disable chroma subsampling. 
+	 */
+	gboolean no_subsample;
+
 } VipsForeignSaveJpeg;
 
 typedef VipsForeignSaveClass VipsForeignSaveJpegClass;
@@ -127,26 +131,33 @@ vips_foreign_save_jpeg_class_init( VipsForeignSaveJpegClass *class )
 		1, 100, 75 );
 
 	VIPS_ARG_STRING( class, "profile", 11, 
-		_( "profile" ), 
+		_( "Profile" ), 
 		_( "ICC profile to embed" ),
 		VIPS_ARGUMENT_OPTIONAL_INPUT,
 		G_STRUCT_OFFSET( VipsForeignSaveJpeg, profile ),
 		NULL );
 
 	VIPS_ARG_BOOL( class, "optimize_coding", 12,
-		_( "optimize_coding" ),
+		_( "Optimize_coding" ),
 		_( "Compute optimal Huffman coding tables" ),
 		VIPS_ARGUMENT_OPTIONAL_INPUT,
 		G_STRUCT_OFFSET( VipsForeignSaveJpeg, optimize_coding ),
 		FALSE );
 
 	VIPS_ARG_BOOL( class, "interlace", 13,
-		_( "interlace" ),
+		_( "Interlace" ),
 		_( "Generate an interlaced (progressive) jpeg" ),
 		VIPS_ARGUMENT_OPTIONAL_INPUT,
 		G_STRUCT_OFFSET( VipsForeignSaveJpeg, interlace ),
 		FALSE );
 
+	VIPS_ARG_BOOL( class, "no_subsample", 14,
+		_( "No subsample" ),
+		_( "Disable chroma subsample" ),
+		VIPS_ARGUMENT_OPTIONAL_INPUT,
+		G_STRUCT_OFFSET( VipsForeignSaveJpeg, no_subsample ),
+		FALSE );
+
 }
 
 static void
@@ -182,7 +193,7 @@ vips_foreign_save_jpeg_file_build( VipsObject *object )
 
 	if( vips__jpeg_write_file( save->ready, file->filename,
 		jpeg->Q, jpeg->profile, jpeg->optimize_coding, 
-		jpeg->interlace, save->strip ) )
+		jpeg->interlace, save->strip, jpeg->no_subsample ) )
 		return( -1 );
 
 	return( 0 );
@@ -248,7 +259,7 @@ vips_foreign_save_jpeg_buffer_build( VipsObject *object )
 
 	if( vips__jpeg_write_buffer( save->ready, 
 		&obuf, &olen, jpeg->Q, jpeg->profile, jpeg->optimize_coding, 
-		jpeg->interlace, save->strip ) )
+		jpeg->interlace, save->strip, jpeg->no_subsample ) )
 		return( -1 );
 
 	area = vips_area_new_blob( (VipsCallbackFn) vips_free, obuf, olen );
@@ -310,7 +321,7 @@ vips_foreign_save_jpeg_mime_build( VipsObject *object )
 
 	if( vips__jpeg_write_buffer( save->ready, 
 		&obuf, &olen, jpeg->Q, jpeg->profile, jpeg->optimize_coding, 
-		jpeg->interlace, save->strip ) )
+		jpeg->interlace, save->strip, jpeg->no_subsample ) )
 		return( -1 );
 
 	printf( "Content-length: %zd\r\n", olen );

libvips/foreign/vips2jpeg.c

@@ -60,6 +60,8 @@
  * 	- add optimize_coding parameter
  * 12/11/13
  * 	- add "strip" option to remove all metadata
+ * 13/11/13
+ * 	- add a "no_subsample" option to disable chroma subsample
  */
 
 /*
@@ -843,7 +845,8 @@ write_jpeg_block( REGION *region, Rect *area, void *a )
  */
 static int
 write_vips( Write *write, int qfac, const char *profile, 
-	gboolean optimize_coding, gboolean progressive, gboolean strip )
+	gboolean optimize_coding, gboolean progressive, gboolean strip, 
+	gboolean no_subsample )
 {
 	VipsImage *in;
 	J_COLOR_SPACE space;
@@ -905,6 +908,17 @@ write_vips( Write *write, int qfac, const char *profile,
 	if( progressive ) 
 		jpeg_simple_progression( &write->cinfo ); 
 
+	/* Turn off chroma subsampling.
+	 */
+	if( no_subsample ) { 
+		int i;
+
+		for( i = 0; i < in->Bands; i++ ) { 
+			write->cinfo.comp_info[i].h_samp_factor = 1;
+			write->cinfo.comp_info[i].v_samp_factor = 1;
+		}
+	}
+
 	/* Build compress tables.
 	 */
 	jpeg_start_compress( &write->cinfo, TRUE );
@@ -952,7 +966,8 @@ write_vips( Write *write, int qfac, const char *profile,
 int
 vips__jpeg_write_file( VipsImage *in, 
 	const char *filename, int Q, const char *profile, 
-	gboolean optimize_coding, gboolean progressive, gboolean strip )
+	gboolean optimize_coding, gboolean progressive, gboolean strip, 
+	gboolean no_subsample )
 {
 	Write *write;
 
@@ -983,7 +998,8 @@ vips__jpeg_write_file( VipsImage *in,
 	/* Convert!
 	 */
 	if( write_vips( write, 
-		Q, profile, optimize_coding, progressive, strip ) ) {
+		Q, profile, optimize_coding, progressive, strip, 
+		no_subsample ) ) {
 		write_destroy( write );
 		return( -1 );
 	}
@@ -1231,7 +1247,7 @@ int
 vips__jpeg_write_buffer( VipsImage *in, 
 	void **obuf, size_t *olen, int Q, const char *profile, 
 	gboolean optimize_coding, gboolean progressive,
-	gboolean strip )
+	gboolean strip, gboolean no_subsample )
 {
 	Write *write;
 
@@ -1261,7 +1277,8 @@ vips__jpeg_write_buffer( VipsImage *in,
 	/* Convert!
 	 */
 	if( write_vips( write, 
-		Q, profile, optimize_coding, progressive, strip ) ) {
+		Q, profile, optimize_coding, progressive, strip, 
+		no_subsample ) ) {
 		write_destroy( write );
 
 		return( -1 );

libvips/foreign/vipsjpeg.h

@@ -39,10 +39,12 @@ extern const char *vips__jpeg_suffs[];
 
 int vips__jpeg_write_file( VipsImage *in, 
 	const char *filename, int Q, const char *profile, 
-	gboolean optimize_coding, gboolean progressive, gboolean strip );
+	gboolean optimize_coding, gboolean progressive, gboolean strip,
+	gboolean no_subsample );
 int vips__jpeg_write_buffer( VipsImage *in, 
 	void **obuf, size_t *olen, int Q, const char *profile, 
-	gboolean optimize_coding, gboolean progressive, gboolean strip );
+	gboolean optimize_coding, gboolean progressive, gboolean strip,
+	gboolean no_subsample );
 
 int vips__isjpeg( const char *filename );
 int vips__jpeg_read_file( const char *name, VipsImage *out,