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Fix alpha-blending with color-mix/blend functions

This commit is contained in:
Elias Batek 2024-05-24 04:44:44 +02:00
parent 511ec3ed6d
commit 5c2817e563
1 changed files with 21 additions and 9 deletions
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30
pixmappaint.d
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@ -7,6 +7,7 @@ module arsd.pixmappaint;
import arsd.color;
import arsd.core;
import std.math : round;
alias Color = arsd.color.Color;
@ -289,8 +290,6 @@ ubyte n255thsOf(const ubyte nPercentage, const ubyte value) {
// Accuracy verification
static ubyte n255thsOfFP64(const ubyte nPercentage, const ubyte value) {
import std.math : round;
return (value * nPercentage / 255.0).round().typeCast!ubyte();
}
@ -333,7 +332,7 @@ void opacity(ref Pixmap pixmap, const ubyte opacity) {
void opacityF(ref Pixmap pixmap, const float opacity)
in (opacity >= 0)
in (opacity <= 1.0) {
immutable opacity255 = typeCast!ubyte(opacity * 255);
immutable opacity255 = round(opacity * 255).typeCast!ubyte;
pixmap.opacity = opacity255;
}
@ -361,6 +360,23 @@ public void alphaBlend(ref Pixel pxTarget, const Pixel pxSource) @trusted {
}
}
///
public void alphaBlend(
ubyte function(const ubyte, const ubyte) blend
)(ref Pixel pxTarget, const Pixel pxSource) @trusted {
pragma(inline, true);
immutable alphaSource = (pxSource.a | (pxSource.a << 8));
immutable alphaTarget = (0xFFFF - alphaSource);
foreach (immutable ib, ref px; pxTarget.components) {
immutable b = blend(px, pxSource.components.ptr[ib]);
immutable d = cast(ubyte)(((px * alphaTarget) + 0x8080) >> 16);
immutable s = cast(ubyte)(((b * alphaSource) + 0x8080) >> 16);
px = cast(ubyte)(d + s);
}
}
// ==== Blending functions ====
enum BlendMode {
@ -396,11 +412,7 @@ void blendPixel(BlendMode mode)(ref Pixel target, const Pixel source) if (mode =
/// ditto
void blendPixel(BlendMode mode)(ref Pixel target, const Pixel source) if (mode == Blend.multiply) {
function(ref Pixel target, const Pixel source) @trusted {
foreach (immutable ib, ref ch; target.components) {
ch = n255thsOf(source.components.ptr[ib], ch);
}
}(target, source);
return alphaBlend!((a, b) => n255thsOf(a, b))(target, source);
}
/// ditto
@ -498,7 +510,7 @@ void drawRectangle(Pixmap target, Rectangle rectangle, Pixel color) {
Draws a line
+/
void drawLine(Pixmap target, Point a, Point b, Pixel color) {
import std.math : round, sqrt;
import std.math : sqrt;
// TODO: line width
// TODO: anti-aliasing (looks awful without it!)