mirror of https://github.com/GNOME/gimp.git
app: change behavior of REPLACE mode for fully-transparent pixels
When the result of compositing has an alpha value of 0, the corresponding color value is not mathematically defined. Currently, all out layer modes opt to preserve the destination's color value in this case. However, REPLACE mode is different enough to warrant a different behavior: Unlike the other layer modes, when the compositing opacity approaches 0 or 1, the output color value approaches the destination or source color values, respectively, regardless of the output alpha value. When the opacity doesn't approach 0 or 1, the output color value generally doesn't approach a limit as the output alpha value approaches 0, however, when both the destination and source alpha values are equal, the output color value is always a simple linear interpolation between the destination and source color values, according to the opacity. In other words, this means that it's reasonable to simply use the above linear interpolation for the output color value, whenever the output alpha value is 0. Since filters are commonly combined with the input using REPALCE mode with full opacity, this has the effect that filters may now modify the color values of fully-transparent pixels. This is generally desirable, IMO, especially for point filters. Indeed, painting with REPLACE mode (i.e., with tools that use gimp_paint_core_replace()) behaved excatly as described above, and had this property, before we switched gimp_paint_core_replace() to use the common compositing code; this created a discrepancy between painting and applying filters, which is now gone. A side effect of this change is that we can now turn gimp:replace into a NOP when the opacity is 100% and there's no mask, which avoids the compositing step when applying filters. We could previously only apply this optimization to PASS_THROUGH mode, which is a subclass of REPLACE mode. Note that the discussion above concerns the UNION composite mode, which is the only mode we currently use REPLACE in. We modify the rest of the composite modes to match the new behavior: CLIP_TO_BACKDROP always preserves the color values of the destionation, CLIP_TO_LAYER always preserves the color values of the source, and INTERSECTION always produces fully-zeroed pixels.
This commit is contained in:
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parent
d2f8413173
commit
27e8f452b3
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@ -25,22 +25,12 @@
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#include "../operations-types.h"
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#include "gimp-layer-modes.h"
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#include "gimpoperationpassthrough.h"
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static gboolean gimp_operation_pass_through_parent_process (GeglOperation *operation,
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GeglOperationContext *context,
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const gchar *output_prop,
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const GeglRectangle *result,
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gint level);
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G_DEFINE_TYPE (GimpOperationPassThrough, gimp_operation_pass_through,
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GIMP_TYPE_OPERATION_REPLACE)
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#define parent_class gimp_operation_pass_through_parent_class
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static void
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gimp_operation_pass_through_class_init (GimpOperationPassThroughClass *klass)
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@ -53,8 +43,6 @@ gimp_operation_pass_through_class_init (GimpOperationPassThroughClass *klass)
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"description", "GIMP pass through mode operation",
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NULL);
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operation_class->process = gimp_operation_pass_through_parent_process;
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/* don't use REPLACE mode's specialized get_affected_region(); PASS_THROUGH
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* behaves like an ordinary layer mode here.
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*/
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@ -65,42 +53,3 @@ static void
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gimp_operation_pass_through_init (GimpOperationPassThrough *self)
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{
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}
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static gboolean
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gimp_operation_pass_through_parent_process (GeglOperation *operation,
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GeglOperationContext *context,
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const gchar *output_prop,
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const GeglRectangle *result,
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gint level)
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{
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GimpOperationLayerMode *layer_mode = (gpointer) operation;
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/* if the layer's opacity is 100%, it has no mask, and its composite mode
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* contains "aux" (the latter should always be the case for pass through
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* mode,) we can just pass "aux" directly as output. note that the same
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* optimization would more generally apply to REPLACE mode, save for the fact
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* that when both the backdrop and the layer have a pixel with 0% alpha, we
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* want to maintain the color value of the backdrop, not the layer; since,
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* for pass through groups, the layer is already composited against the
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* backdrop, such pixels will have the same color value for both the backdrop
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* and the layer.
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*/
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if (layer_mode->opacity == 1.0 &&
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! gegl_operation_context_get_object (context, "aux2") &&
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(gimp_layer_mode_get_included_region (layer_mode->layer_mode,
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layer_mode->real_composite_mode) &
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GIMP_LAYER_COMPOSITE_REGION_SOURCE))
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{
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GObject *aux;
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aux = gegl_operation_context_get_object (context, "aux");
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gegl_operation_context_set_object (context, "output", aux);
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return TRUE;
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}
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return GEGL_OPERATION_CLASS (parent_class)->process (operation, context,
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output_prop, result,
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level);
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}
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@ -24,9 +24,16 @@
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#include "../operations-types.h"
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#include "gimp-layer-modes.h"
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#include "gimpoperationreplace.h"
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static gboolean gimp_operation_replace_parent_process (GeglOperation *op,
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GeglOperationContext *context,
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const gchar *output_prop,
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const GeglRectangle *result,
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gint level);
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static gboolean gimp_operation_replace_process (GeglOperation *op,
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void *in,
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void *layer,
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@ -41,6 +48,8 @@ static GimpLayerCompositeRegion gimp_operation_replace_get_affected_region (Gi
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G_DEFINE_TYPE (GimpOperationReplace, gimp_operation_replace,
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GIMP_TYPE_OPERATION_LAYER_MODE)
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#define parent_class gimp_operation_replace_parent_class
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static void
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gimp_operation_replace_class_init (GimpOperationReplaceClass *klass)
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@ -53,6 +62,8 @@ gimp_operation_replace_class_init (GimpOperationReplaceClass *klass)
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"description", "GIMP replace mode operation",
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NULL);
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operation_class->process = gimp_operation_replace_parent_process;
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layer_mode_class->process = gimp_operation_replace_process;
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layer_mode_class->get_affected_region = gimp_operation_replace_get_affected_region;
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}
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@ -62,6 +73,41 @@ gimp_operation_replace_init (GimpOperationReplace *self)
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{
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}
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static gboolean
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gimp_operation_replace_parent_process (GeglOperation *op,
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GeglOperationContext *context,
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const gchar *output_prop,
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const GeglRectangle *result,
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gint level)
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{
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GimpOperationLayerMode *layer_mode = (gpointer) op;
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/* if the layer's opacity is 100%, it has no mask, and its composite mode
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* contains "aux" (the latter should always be the case in practice,
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* currently,) we can just pass "aux" directly as output.
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*/
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if (layer_mode->opacity == 1.0 &&
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! gegl_operation_context_get_object (context, "aux2") &&
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(gimp_layer_mode_get_included_region (layer_mode->layer_mode,
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layer_mode->real_composite_mode) &
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GIMP_LAYER_COMPOSITE_REGION_SOURCE))
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{
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GObject *aux;
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aux = gegl_operation_context_get_object (context, "aux");
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gegl_operation_context_set_object (context, "output", aux);
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return TRUE;
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}
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/* the opposite case, where the opacity is 0%, is handled by
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* GimpOperationLayerMode.
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*/
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return GEGL_OPERATION_CLASS (parent_class)->process (op, context, output_prop,
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result, level);
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}
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static gboolean
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gimp_operation_replace_process (GeglOperation *op,
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void *in_p,
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@ -88,6 +134,7 @@ gimp_operation_replace_process (GeglOperation *op,
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{
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gfloat opacity_value = opacity;
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gfloat new_alpha;
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gfloat ratio;
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gint b;
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if (has_mask)
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@ -95,18 +142,13 @@ gimp_operation_replace_process (GeglOperation *op,
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new_alpha = (layer[ALPHA] - in[ALPHA]) * opacity_value + in[ALPHA];
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if (new_alpha)
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{
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gfloat ratio = opacity_value * layer[ALPHA] / new_alpha;
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ratio = opacity_value;
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for (b = RED; b < ALPHA; b++)
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out[b] = (layer[b] - in[b]) * ratio + in[b];
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}
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else
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{
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for (b = RED; b < ALPHA; b++)
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out[b] = in[b];
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}
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if (new_alpha)
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ratio *= layer[ALPHA] / new_alpha;
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for (b = RED; b < ALPHA; b++)
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out[b] = (layer[b] - in[b]) * ratio + in[b];
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out[ALPHA] = new_alpha;
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@ -136,8 +178,8 @@ gimp_operation_replace_process (GeglOperation *op,
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out[ALPHA] = new_alpha;
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in += 4;
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out += 4;
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in += 4;
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out += 4;
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if (has_mask)
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mask++;
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@ -156,16 +198,8 @@ gimp_operation_replace_process (GeglOperation *op,
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new_alpha = layer[ALPHA] * opacity_value;
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if (new_alpha)
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{
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for (b = RED; b < ALPHA; b++)
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out[b] = layer[b];
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}
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else
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{
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for (b = RED; b < ALPHA; b++)
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out[b] = in[b];
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}
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for (b = RED; b < ALPHA; b++)
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out[b] = layer[b];
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out[ALPHA] = new_alpha;
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@ -179,18 +213,7 @@ gimp_operation_replace_process (GeglOperation *op,
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break;
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case GIMP_LAYER_COMPOSITE_INTERSECTION:
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while (samples--)
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{
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gint b;
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for (b = RED; b < ALPHA; b++)
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out[b] = in[b];
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out[ALPHA] = 0.0f;
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in += 4;
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out += 4;
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}
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memset (out, 0, 4 * samples * sizeof (gfloat));
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break;
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}
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