fix up docs
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John Cupitt
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b5944ef464
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05acd06661
@ -57,6 +57,8 @@ typedef struct _VipsPremultiply {
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VipsImage *in;
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double max_alpha;
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} VipsPremultiply;
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typedef VipsConversionClass VipsPremultiplyClass;
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@ -71,12 +73,12 @@ G_DEFINE_TYPE( VipsPremultiply, vips_premultiply, VIPS_TYPE_CONVERSION );
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\
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for( x = 0; x < width; x++ ) { \
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IN alpha = p[bands - 1]; \
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int clip_alpha = VIPS_CLIP( 0, alpha, max_value ); \
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double nalpha = (double) clip_alpha / max_value; \
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IN clip_alpha = VIPS_CLIP( 0, alpha, max_alpha ); \
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double nalpha = (double) clip_alpha / max_alpha; \
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\
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for( b = 0; b < bands - 1; b++ ) \
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q[b] = p[b] * nalpha; \
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q[b] = alpha; \
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for( i = 0; i < bands - 1; i++ ) \
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q[i] = p[i] * nalpha; \
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q[i] = alpha; \
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\
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p += bands; \
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q += bands; \
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@ -91,8 +93,8 @@ G_DEFINE_TYPE( VipsPremultiply, vips_premultiply, VIPS_TYPE_CONVERSION );
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\
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for( x = 0; x < width; x++ ) { \
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IN alpha = p[3]; \
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int clip_alpha = VIPS_CLIP( 0, alpha, max_value ); \
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double nalpha = (double) clip_alpha / max_value; \
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IN clip_alpha = VIPS_CLIP( 0, alpha, max_alpha ); \
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double nalpha = (double) clip_alpha / max_alpha; \
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\
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q[0] = p[0] * nalpha; \
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q[1] = p[1] * nalpha; \
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@ -117,24 +119,19 @@ static int
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vips_premultiply_gen( VipsRegion *or, void *vseq, void *a, void *b,
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gboolean *stop )
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{
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VipsPremultiply *premultiply = (VipsPremultiply *) b;
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VipsRegion *ir = (VipsRegion *) vseq;
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VipsImage *im = ir->im;
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VipsRect *r = &or->valid;
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int width = r->width;
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int bands = im->Bands;
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double max_alpha = premultiply->max_alpha;
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int max_value;
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int x, y, b;
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int x, y, i;
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if( vips_region_prepare( ir, r ) )
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return( -1 );
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if( im->Type == VIPS_INTERPRETATION_GREY16 ||
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im->Type == VIPS_INTERPRETATION_RGB16 )
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max_value = 65535;
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else
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max_value = 255;
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for( y = 0; y < r->height; y++ ) {
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VipsPel *in = VIPS_REGION_ADDR( ir, r->left, r->top + y );
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VipsPel *out = VIPS_REGION_ADDR( or, r->left, r->top + y );
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@ -252,11 +249,18 @@ vips_premultiply_class_init( VipsPremultiplyClass *class )
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VIPS_ARGUMENT_REQUIRED_INPUT,
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G_STRUCT_OFFSET( VipsPremultiply, in ) );
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VIPS_ARG_DOUBLE( class, "max_alpha", 115,
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_( "Maximum value" ),
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_( "Maximum value of alpha channel" ),
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VIPS_ARGUMENT_OPTIONAL_INPUT,
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G_STRUCT_OFFSET( VipsPremultiply, max_alpha ),
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0, 100000000, 255 );
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}
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static void
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vips_premultiply_init( VipsPremultiply *premultiply )
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{
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premultiply->max_alpha = 255.0;
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}
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/**
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@ -265,25 +269,32 @@ vips_premultiply_init( VipsPremultiply *premultiply )
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* @out: output image
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* @...: %NULL-terminated list of optional named arguments
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*
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* Premultiplies any alpha channel. If @in is an 8-bit RGBA image, @out will
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* also have four bands, where:
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* Optional arguments:
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*
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* @max_alpha: %gdouble, maximum value for alpha
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*
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* Premultiplies any alpha channel.
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* The final band is taken to be the alpha
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* and the bands are transformed as:
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*
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* |[
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* n = in[3] / 255.0; // normalised alpha
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* out = [in[0] * n, in[1] * n, in[2] * n, in[3]];
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* alpha = clip( 0, in[in.bands - 1], @max_alpha );
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* norm = alpha / @max_alpha;
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* out = [in[0] * norm, ..., in[in.bands - 1] * norm, alpha];
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* |]
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*
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* So the RGB bands are scaled by alpha, alpha is untouched.
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* So for an N-band image, the first N - 1 bands are multiplied by the clipped
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* and normalised final band, the final band is clipped.
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* If there is only a single band,
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* the image is passed through unaltered.
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*
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* The result is
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* #VIPS_FORMAT_FLOAT unless the input format is #VIPS_FORMAT_DOUBLE, in which
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* case the output is double as well.
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* If there is no alpha,
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* the image is passed through unaltered.
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*
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* The operation works for 1 - 5 band images, from greyscale to CMYKA.
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* If interpretation is #VIPS_INTERPRETATION_GREY16 or
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* #VIPS_INTERPRETATION_RGB16, alpha is assumed to have a 0 - 65535 range.
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* Otherwise alpha is assumed to have a 0 - 255 range.
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* @max_alpha has the default value 255. You will need to set this to 65535
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* for images with a 16-bit alpha, or perhaps 1.0 for images with a float
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* alpha.
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*
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* See also: vips_unpremultiply(), vips_flatten().
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*
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@ -57,6 +57,8 @@ typedef struct _VipsUnpremultiply {
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VipsImage *in;
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double max_alpha;
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} VipsUnpremultiply;
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typedef VipsConversionClass VipsUnpremultiplyClass;
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@ -65,36 +67,38 @@ G_DEFINE_TYPE( VipsUnpremultiply, vips_unpremultiply, VIPS_TYPE_CONVERSION );
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/* Unpremultiply a greyscale (two band) image.
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*/
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#define UNPRE_GREY( IN, OUT ) { \
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#define UNPRE_MANY( IN, OUT ) { \
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IN * restrict p = (IN *) in; \
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OUT * restrict q = (OUT *) out; \
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\
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for( x = 0; x < width; x++ ) { \
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IN alpha = p[1]; \
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int clip_alpha = VIPS_CLIP( 0, alpha, max_value ); \
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double nalpha = (double) clip_alpha / max_value; \
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IN alpha = p[bands - 1]; \
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int clip_alpha = VIPS_CLIP( 0, alpha, max_alpha ); \
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double nalpha = (double) clip_alpha / max_alpha; \
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\
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if( clip_alpha == 0 ) \
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q[0] = 0; \
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for( i = 0; i < bands - 1; i++ ) \
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q[i] = 0; \
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else \
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q[0] = p[0] / nalpha; \
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q[1] = clip_alpha; \
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for( i = 0; i < bands - 1; i++ ) \
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q[i] = p[i] / nalpha; \
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q[i] = clip_alpha; \
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\
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p += 2; \
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q += 2; \
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p += bands; \
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q += bands; \
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} \
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}
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/* Unpremultiply an RGB (four band) image.
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*/
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#define UNPRE_RGB( IN, OUT ) { \
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#define UNPRE_RGBA( IN, OUT ) { \
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IN * restrict p = (IN *) in; \
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OUT * restrict q = (OUT *) out; \
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\
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for( x = 0; x < width; x++ ) { \
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IN alpha = p[3]; \
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int clip_alpha = VIPS_CLIP( 0, alpha, max_value ); \
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double nalpha = (double) clip_alpha / max_value; \
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int clip_alpha = VIPS_CLIP( 0, alpha, max_alpha ); \
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double nalpha = (double) clip_alpha / max_alpha; \
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\
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if( clip_alpha == 0 ) { \
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q[0] = 0; \
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@ -113,45 +117,12 @@ G_DEFINE_TYPE( VipsUnpremultiply, vips_unpremultiply, VIPS_TYPE_CONVERSION );
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} \
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}
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/* Unpremultiply a CMYK (five band) image.
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*/
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#define UNPRE_CMYK( IN, OUT ) { \
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IN * restrict p = (IN *) in; \
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OUT * restrict q = (OUT *) out; \
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\
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for( x = 0; x < width; x++ ) { \
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IN alpha = p[4]; \
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int clip_alpha = VIPS_CLIP( 0, alpha, max_value ); \
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double nalpha = (double) clip_alpha / max_value; \
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\
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if( clip_alpha == 0 ) { \
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q[0] = 0; \
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q[1] = 0; \
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q[2] = 0; \
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q[3] = 0; \
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} \
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else { \
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q[0] = p[0] / nalpha; \
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q[1] = p[1] / nalpha; \
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q[2] = p[2] / nalpha; \
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q[3] = p[3] / nalpha; \
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} \
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q[4] = clip_alpha; \
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\
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p += 5; \
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q += 5; \
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} \
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}
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#define UNPRE( IN, OUT ) { \
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if( bands == 2 ) { \
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UNPRE_GREY( IN, OUT ); \
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} \
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else if( bands == 4 ) { \
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UNPRE_RGB( IN, OUT ); \
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if( bands == 4 ) { \
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UNPRE_RGBA( IN, OUT ); \
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} \
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else { \
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UNPRE_CMYK( IN, OUT ); \
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UNPRE_MANY( IN, OUT ); \
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} \
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}
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@ -159,24 +130,19 @@ static int
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vips_unpremultiply_gen( VipsRegion *or, void *vseq, void *a, void *b,
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gboolean *stop )
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{
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VipsUnpremultiply *unpremultiply = (VipsUnpremultiply *) b;
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VipsRegion *ir = (VipsRegion *) vseq;
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VipsImage *im = ir->im;
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VipsRect *r = &or->valid;
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int width = r->width;
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int bands = im->Bands;
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double max_alpha = unpremultiply->max_alpha;
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int max_value;
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int x, y;
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int x, y, i;
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if( vips_region_prepare( ir, r ) )
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return( -1 );
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if( im->Type == VIPS_INTERPRETATION_GREY16 ||
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im->Type == VIPS_INTERPRETATION_RGB16 )
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max_value = 65535;
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else
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max_value = 255;
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for( y = 0; y < r->height; y++ ) {
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VipsPel *in = VIPS_REGION_ADDR( ir, r->left, r->top + y );
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VipsPel *out = VIPS_REGION_ADDR( or, r->left, r->top + y );
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@ -247,10 +213,7 @@ vips_unpremultiply_build( VipsObject *object )
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/* Trivial case: fall back to copy().
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*/
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if( in->Bands == 1 ||
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in->Bands == 3 ||
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(in->Bands == 4 &&
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in->Type == VIPS_INTERPRETATION_CMYK) )
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if( in->Bands == 1 )
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return( vips_image_write( in, conversion->out ) );
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if( vips_check_noncomplex( class->nickname, in ) )
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@ -297,11 +260,19 @@ vips_unpremultiply_class_init( VipsUnpremultiplyClass *class )
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VIPS_ARGUMENT_REQUIRED_INPUT,
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G_STRUCT_OFFSET( VipsUnpremultiply, in ) );
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VIPS_ARG_DOUBLE( class, "max_alpha", 115,
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_( "Maximum value" ),
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_( "Maximum value of alpha channel" ),
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VIPS_ARGUMENT_OPTIONAL_INPUT,
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G_STRUCT_OFFSET( VipsUnpremultiply, max_alpha ),
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0, 100000000, 255 );
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}
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static void
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vips_unpremultiply_init( VipsUnpremultiply *unpremultiply )
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{
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unpremultiply->max_alpha = 255.0;
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}
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/**
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@ -310,29 +281,35 @@ vips_unpremultiply_init( VipsUnpremultiply *unpremultiply )
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* @out: output image
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* @...: %NULL-terminated list of optional named arguments
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*
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* Unpremultiplies any alpha channel. If @in is a four-band RGBA image, @out
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* will also have four bands, where:
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* Optional arguments:
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*
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* @max_alpha: %gdouble, maximum value for alpha
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*
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* Unpremultiplies any alpha channel.
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* The final band is taken to be the alpha
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* and the bands are transformed as:
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*
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* |[
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* alpha = (unsigned char) clip( 0, in[3], 255 ); // clip alphha range
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* n = alpha / 255; // normalised alpha
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* if( n == 0 )
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* out = [0, 0, 0, in[3]];
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* alpha = (int) clip( 0, in[in.bands - 1], @max_alpha );
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* norm = (double) alpha / @max_alpha;
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* if( alpha == 0 )
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* out = [0, ..., 0, alpha];
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* else
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* out = [in[0] / n, in[1] / n, in[2] / n, in[3]];
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* out = [in[0] / norm, ..., in[in.bands - 1] / norm, alpha];
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* |]
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*
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* So the RGB bands are divided by alpha, alpha is untouched.
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* So for an N-band image, the first N - 1 bands are divided by the clipped
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* and normalised final band, the final band is clipped.
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* If there is only a single band,
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* the image is passed through unaltered.
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*
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* The result is
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* #VIPS_FORMAT_FLOAT unless the input format is #VIPS_FORMAT_DOUBLE, in which
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* case the output is double as well.
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* If there is no alpha,
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* the image is passed through unaltered.
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*
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* The operation works for 1 - 5 band images, from greyscale to CMYKA.
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* If interpretation is #VIPS_INTERPRETATION_GREY16 or
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* #VIPS_INTERPRETATION_RGB16, alpha is assumed to have a 0 - 65535 range.
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* Otherwise alpha is assumed to have a 0 - 255 range.
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* @max_alpha has the default value 255. You will need to set this to 65535
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* for images with a 16-bit alpha, or perhaps 1.0 for images with a float
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* alpha.
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*
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* See also: vips_premultiply(), vips_flatten().
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*
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