Add 8bpp PNG quantization support
This adds support for saving 8-Bit one band palette based PNG images with palette based alpha channel (often called PNG8+Alpha). The image is first converted to sRGBA and then quantized using libimagequant controlled by the colors, Q and dither params.
This commit is contained in:
Felix Bünemann
parent
b5531cf1ed
commit
d9d2f7b89a
@ -197,10 +197,11 @@ int vips__png_header_buffer( const void *buffer, size_t length, VipsImage *out )
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int vips__png_write( VipsImage *in, const char *filename,
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int compress, int interlace, const char *profile,
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VipsForeignPngFilter filter, gboolean strip );
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VipsForeignPngFilter filter, gboolean strip, int colors, int Q, double dither );
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int vips__png_write_buf( VipsImage *in,
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void **obuf, size_t *olen, int compression, int interlace,
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const char *profile, VipsForeignPngFilter filter, gboolean strip );
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const char *profile, VipsForeignPngFilter filter, gboolean strip,
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int colors, int Q, double dither );
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/* Map WEBP metadata names to vips names.
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*/
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@ -60,6 +60,9 @@ typedef struct _VipsForeignSavePng {
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gboolean interlace;
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char *profile;
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VipsForeignPngFilter filter;
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int colors;
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int Q;
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double dither;
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} VipsForeignSavePng;
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typedef VipsForeignSaveClass VipsForeignSavePngClass;
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@ -133,6 +136,27 @@ vips_foreign_save_png_class_init( VipsForeignSavePngClass *class )
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VIPS_TYPE_FOREIGN_PNG_FILTER,
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VIPS_FOREIGN_PNG_FILTER_ALL );
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VIPS_ARG_INT( class, "colors", 13,
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_( "Colors" ),
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_( "Number of palette entries" ),
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VIPS_ARGUMENT_OPTIONAL_INPUT,
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G_STRUCT_OFFSET( VipsForeignSavePng, colors ),
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2, 256, 256 );
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VIPS_ARG_INT( class, "Q", 14,
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_( "Q" ),
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_( "Q factor" ),
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VIPS_ARGUMENT_OPTIONAL_INPUT,
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G_STRUCT_OFFSET( VipsForeignSavePng, Q ),
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0, 100, 75 );
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VIPS_ARG_DOUBLE( class, "dither", 15,
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_( "Dithering" ),
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_( "Amount of dithering" ),
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VIPS_ARGUMENT_OPTIONAL_INPUT,
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G_STRUCT_OFFSET( VipsForeignSavePng, dither ),
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0.0, 1.0, 1.0 );
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}
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static void
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@ -140,6 +164,9 @@ vips_foreign_save_png_init( VipsForeignSavePng *png )
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{
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png->compression = 6;
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png->filter = VIPS_FOREIGN_PNG_FILTER_ALL;
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png->colors = 0;
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png->Q = 75;
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png->dither = 1.0;
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}
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typedef struct _VipsForeignSavePngFile {
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@ -166,7 +193,8 @@ vips_foreign_save_png_file_build( VipsObject *object )
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if( vips__png_write( save->ready,
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png_file->filename, png->compression, png->interlace,
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png->profile, png->filter, save->strip ) )
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png->profile, png->filter, save->strip, png->colors, png->Q,
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png->dither ) )
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return( -1 );
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return( 0 );
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@ -225,7 +253,7 @@ vips_foreign_save_png_buffer_build( VipsObject *object )
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if( vips__png_write_buf( save->ready, &obuf, &olen,
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png->compression, png->interlace, png->profile, png->filter,
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save->strip ) )
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save->strip, png->colors, png->Q, png->dither ) )
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return( -1 );
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/* vips__png_write_buf() makes a buffer that needs g_free(), not
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@ -278,6 +306,9 @@ vips_foreign_save_png_buffer_init( VipsForeignSavePngBuffer *buffer )
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* * @interlace: interlace image
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* * @profile: ICC profile to embed
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* * @filter: #VipsForeignPngFilter row filter flag(s)
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* * @colors: enable 8bpp quantization with max n colors
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* * @Q: quality for 8bpp quantization (does not exceed @colors)
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* * @dither: amount of dithering for 8bpp quantization
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*
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* Write a VIPS image to a file as PNG.
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*
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@ -304,6 +335,13 @@ vips_foreign_save_png_buffer_init( VipsForeignSavePngBuffer *buffer )
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* alpha before saving. Images with more than one byte per band element are
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* saved as 16-bit PNG, others are saved as 8-bit PNG.
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*
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* If @colors is given, it limits the maximum number of colors in the image
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* and the source image will be quantized down to an 8-Bit one band indexed
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* image with palette based alpha transparency. Similar to JPEG the quality
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* can be controlled with the @Q parameter and the amount of Floyd-Steinberg
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* dithering is set with @dither.
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* This feature requires libvips to be compiled with libimagequant.
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*
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* See also: vips_image_new_from_file().
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*
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* Returns: 0 on success, -1 on error.
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@ -124,6 +124,10 @@
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#error "PNG library too old."
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#endif
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#ifdef HAVE_IMAGEQUANT
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#include <libimagequant.h>
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#endif
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static void
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user_error_function( png_structp png_ptr, png_const_charp error_msg )
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{
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@ -877,12 +881,110 @@ write_png_block( VipsRegion *region, VipsRect *area, void *a )
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return( 0 );
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}
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#ifdef HAVE_IMAGEQUANT
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static int
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quantize_image( VipsImage *in, VipsImage *out, VipsImage *palette_out,
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int colors, int Q, double dither )
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{
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/* Ensure input is sRGB. */
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if( in->Type != VIPS_INTERPRETATION_sRGB) {
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VipsImage *srgb;
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if( vips_colourspace( in, &srgb, VIPS_INTERPRETATION_sRGB,
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NULL ) )
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return( -1 );
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in = srgb;
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VIPS_UNREF( srgb );
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}
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/* Add alpha channel if missing. */
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if( in->Bands == 3 ) {
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VipsImage *srgba;
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if( vips_bandjoin_const1( in, &srgba, 255, NULL ) )
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return( -1 );
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in = srgba;
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VIPS_UNREF( srgba );
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}
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VipsImage *memory;
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if( !(memory = vips_image_copy_memory( in )) )
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return( -1 );
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in = memory;
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liq_attr *attr = liq_attr_create();
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liq_set_max_colors( attr, colors );
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liq_set_quality( attr, 0, Q );
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liq_image *input_image = liq_image_create_rgba( attr,
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VIPS_IMAGE_ADDR( in, 0, 0 ), in->Xsize, in->Ysize, 0 );
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liq_result *quantization_result;
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if ( liq_image_quantize( input_image, attr, &quantization_result ) ) {
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liq_result_destroy( quantization_result );
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liq_image_destroy( input_image );
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liq_attr_destroy( attr );
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VIPS_UNREF( memory );
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return( -1 );
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}
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liq_set_dithering_level( quantization_result, (float) dither );
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vips_image_init_fields( out, in->Xsize, in->Ysize, 1, VIPS_FORMAT_UCHAR,
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VIPS_CODING_NONE, VIPS_INTERPRETATION_B_W, 1.0, 1.0 );
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if( vips_image_write_prepare( out ) ) {
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liq_result_destroy( quantization_result );
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liq_image_destroy( input_image );
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liq_attr_destroy( attr );
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VIPS_UNREF( memory );
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return( -1 );
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}
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if( liq_write_remapped_image( quantization_result, input_image,
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VIPS_IMAGE_ADDR( out, 0, 0 ), VIPS_IMAGE_N_PELS( out ) ) ) {
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liq_result_destroy( quantization_result );
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liq_image_destroy( input_image );
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liq_attr_destroy( attr );
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VIPS_UNREF( memory );
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return( -1 );
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}
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const liq_palette *palette = liq_get_palette( quantization_result );
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vips_image_init_fields( palette_out, palette->count, 1, 4,
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VIPS_FORMAT_UCHAR, VIPS_CODING_NONE, VIPS_INTERPRETATION_sRGB,
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1.0, 1.0 );
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if( vips_image_write_prepare( palette_out ) ) {
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liq_result_destroy( quantization_result );
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liq_image_destroy( input_image );
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liq_attr_destroy( attr );
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VIPS_UNREF( memory );
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return( -1 );
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}
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int i;
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for( i = 0; i < palette->count; i++ ) {
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unsigned char *p = VIPS_IMAGE_ADDR( palette_out, i, 0 );
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p[0] = palette->entries[i].r;
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p[1] = palette->entries[i].g;
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p[2] = palette->entries[i].b;
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p[3] = palette->entries[i].a;
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}
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liq_result_destroy( quantization_result );
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liq_image_destroy( input_image );
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liq_attr_destroy( attr );
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VIPS_UNREF( memory );
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return( 0 );
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}
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#endif
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/* Write a VIPS image to PNG.
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*/
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static int
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write_vips( Write *write,
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int compress, int interlace, const char *profile,
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VipsForeignPngFilter filter, gboolean strip )
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VipsForeignPngFilter filter, gboolean strip, int colors, int Q,
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double dither )
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{
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VipsImage *in = write->in;
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@ -942,6 +1044,19 @@ write_vips( Write *write,
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return( -1 );
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}
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#ifdef HAVE_IMAGEQUANT
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/* Enable image quantization to paletted 8bpp PNG if colors is set.
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*/
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if( colors ) {
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g_assert( colors >= 2 && colors <= 256 );
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bit_depth = 8;
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color_type = PNG_COLOR_TYPE_PALETTE;
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}
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#else
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if( colors )
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g_warning( "%s", _( "ignoring colors" ) );
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#endif
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interlace_type = interlace ? PNG_INTERLACE_ADAM7 : PNG_INTERLACE_NONE;
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png_set_IHDR( write->pPng, write->pInfo,
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@ -994,7 +1109,66 @@ write_vips( Write *write,
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PNG_COMPRESSION_TYPE_BASE, data, length );
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}
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png_write_info( write->pPng, write->pInfo );
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#ifdef HAVE_IMAGEQUANT
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if( colors ) {
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VipsImage *quantized = vips_image_new_memory();
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VipsImage *palette = vips_image_new_memory();
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if( quantize_image( in, quantized, palette, colors, Q,
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dither ) ) {
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vips_error( "vips2png",
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"%s", _( "quantization failed" ) );
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VIPS_UNREF( quantized );
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VIPS_UNREF( palette );
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return( -1 );
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}
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int palette_count = palette->Xsize;
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g_assert( palette_count <= PNG_MAX_PALETTE_LENGTH);
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png_color *png_palette = (png_color *) png_malloc( write->pPng,
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palette_count * sizeof( png_color ) );
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png_byte *png_trans = (png_byte *) png_malloc( write->pPng,
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palette_count * sizeof( png_byte ) );
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int trans_count = 0;
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for( i = 0; i < palette_count; i++ ) {
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png_byte *p = (png_byte *) VIPS_IMAGE_ADDR( palette, i,
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0 );
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png_color *col = &png_palette[i];
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col->red = p[0];
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col->green = p[1];
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col->blue = p[2];
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png_trans[i] = p[3];
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if( p[3] != 255 )
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trans_count = i + 1;
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#ifdef DEBUG
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printf( "write_vips: palette[%d] %d %d %d %d\n",
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i + 1, p[0], p[1], p[2], p[3] );
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#endif /*DEBUG*/
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}
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#ifdef DEBUG
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printf( "write_vips: attaching %d color palette\n",
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palette_count );
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#endif /*DEBUG*/
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png_set_PLTE( write->pPng, write->pInfo, png_palette,
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palette_count );
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if( trans_count ) {
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#ifdef DEBUG
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printf( "write_vips: attaching %d alpha values\n",
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trans_count );
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#endif /*DEBUG*/
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png_set_tRNS( write->pPng, write->pInfo, png_trans,
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trans_count, NULL );
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}
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VIPS_UNREF( palette );
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VIPS_UNREF( write->memory );
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write->memory = quantized;
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in = write->memory;
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}
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#endif
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png_write_info( write->pPng, write->pInfo );
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/* If we're an intel byte order CPU and this is a 16bit image, we need
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* to swap bytes.
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@ -1027,7 +1201,8 @@ write_vips( Write *write,
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int
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vips__png_write( VipsImage *in, const char *filename,
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int compress, int interlace, const char *profile,
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VipsForeignPngFilter filter, gboolean strip )
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VipsForeignPngFilter filter, gboolean strip,
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int colors, int Q, double dither )
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{
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Write *write;
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@ -1047,7 +1222,8 @@ vips__png_write( VipsImage *in, const char *filename,
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/* Convert it!
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*/
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if( write_vips( write,
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compress, interlace, profile, filter, strip ) ) {
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compress, interlace, profile, filter, strip, colors, Q,
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dither ) ) {
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vips_error( "vips2png",
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_( "unable to write \"%s\"" ), filename );
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@ -1074,7 +1250,8 @@ user_write_data( png_structp png_ptr, png_bytep data, png_size_t length )
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int
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vips__png_write_buf( VipsImage *in,
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void **obuf, size_t *olen, int compression, int interlace,
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const char *profile, VipsForeignPngFilter filter, gboolean strip )
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const char *profile, VipsForeignPngFilter filter, gboolean strip,
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int colors, int Q, double dither )
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{
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Write *write;
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@ -1086,7 +1263,8 @@ vips__png_write_buf( VipsImage *in,
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/* Convert it!
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*/
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if( write_vips( write,
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compression, interlace, profile, filter, strip ) ) {
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compression, interlace, profile, filter, strip, colors, Q,
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dither ) ) {
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vips_error( "vips2png",
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"%s", _( "unable to write to buffer" ) );
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@ -196,7 +196,8 @@ if test_supported tiffload; then
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fi
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if test_supported pngload; then
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test_format $image png 0
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test_format $image png 0 [compression=9,interlace=1]
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test_format $image png 0 [compression=9,interlace=1]
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test_format $image png 90 [colors=256,Q=100,dither=0,compression=9,interlace=1]
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fi
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if test_supported jpegload; then
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test_format $image jpg 90
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