Add mask invert operator

Sources/arm/Layers.hx

@@ -30,6 +30,7 @@ class Layers {
 	public static var pipeCopy8: PipelineState;
 	public static var pipeCopy128: PipelineState;
 	public static var pipeCopyBGRA: PipelineState;
+	public static var pipeInvert8: PipelineState;
 	public static var pipeMask: PipelineState;
 	public static var tex0: TextureUnit;
 	public static var tex1: TextureUnit;
@@ -186,6 +187,18 @@ class Layers {
 		pipeCopy128 = pipeCopy;
 		#end
 
+		pipeInvert8 = new PipelineState();
+		pipeInvert8.vertexShader = Reflect.field(kha.Shaders, "layer_view_vert");
+		pipeInvert8.fragmentShader = Reflect.field(kha.Shaders, "layer_invert_frag");
+		var vs = new VertexStructure();
+		vs.add("pos", VertexData.Float3);
+		vs.add("tex", VertexData.Float2);
+		vs.add("col", VertexData.Float4);
+		pipeInvert8.inputLayout = [vs];
+		pipeCopy8.colorAttachmentCount = 1;
+		pipeCopy8.colorAttachments[0] = TextureFormat.L8;
+		pipeInvert8.compile();
+
 		pipeMask = new PipelineState();
 		pipeMask.vertexShader = Reflect.field(kha.Shaders, "layer_merge_vert");
 		pipeMask.fragmentShader = Reflect.field(kha.Shaders, "mask_merge_frag");

Sources/arm/data/LayerSlot.hx

@@ -210,6 +210,20 @@ class LayerSlot {
 		Context.ddirty = 3;
 	}
 
+	public function invertMask() {
+		if (Layers.pipeInvert8 == null) Layers.makePipe();
+		var inverted = Image.createRenderTarget(texpaint_mask.width, texpaint_mask.height, TextureFormat.L8);
+		inverted.g2.begin(false);
+		inverted.g2.pipeline = Layers.pipeInvert8;
+		inverted.g2.drawImage(texpaint_mask, 0, 0);
+		inverted.g2.pipeline = null;
+		inverted.g2.end();
+		texpaint_mask.unload();
+		texpaint_mask = RenderPath.active.renderTargets.get("texpaint_mask" + id).image = inverted;
+		Context.layerPreviewDirty = true;
+		Context.ddirty = 3;
+	}
+
 	public function deleteMask() {
 		if (texpaint_mask == null) return;
 

Sources/arm/ui/TabLayers.hx

@@ -227,6 +227,15 @@ class TabLayers {
 								}
 								iron.App.notifyOnRender(clear);
 							}
+							if (ui.button(tr("Invert"), Left)) {
+								function invert(g: kha.graphics4.Graphics) {
+									g.end();
+									l.invertMask();
+									g.begin();
+									iron.App.removeRender(invert);
+								}
+								iron.App.notifyOnRender(invert);
+							}
 							if (ui.button(tr("Apply"), Left)) {
 								function makeApply(g: kha.graphics4.Graphics) {
 									g.end();
@@ -239,7 +248,7 @@ class TabLayers {
 								}
 								iron.App.notifyOnRender(makeApply);
 							}
-						}, 5);
+						}, 6);
 					}
 					if (state == State.Started) {
 						Context.setLayer(l, true);