add blend mode, clear canvas before redraw, various improvements

src/collages.ts

@@ -1,7 +1,13 @@
 import {CollageMode} from "@/types";
-import {randint, shuffle} from "@/utils";
+import {choice, randint, shuffle} from "@/utils";
 
-const collageModeType = ["clean_grid", "chaos_grid", "row", "irow", "col", "icol", "concentric_factor", "concentric_spaced"] as const;
+const collageModeType = [
+    "clean_grid", "chaos_grid",
+    "row", "irow",
+    "col", "icol",
+    "concentric_factor", "concentric_spaced",
+    "blend"
+] as const;
 export type CollageModeType = typeof collageModeType[number];
 
 function cleanDraw(ctx: CanvasRenderingContext2D, image: ImageBitmap,
@@ -140,8 +146,7 @@ const modes: { [key in CollageModeType]: CollageMode } = {
 
             let factor: number;
             if (Math.random() > .5) {
-                const factors = [1 / Math.sqrt(2), .5, .88];
-                factor = factors[Math.floor(Math.random() * factors.length)];
+                factor = choice([1 / Math.sqrt(2), .5, .88]);
             } else {
                 factor = 1 - (1 / selectedImages.length);
             }
@@ -156,17 +161,32 @@ const modes: { [key in CollageModeType]: CollageMode } = {
         minImages: 2,
         place: (ctx, images, config) => {
             const selectedImages = shuffle(images).slice(0, config.numImages || randint(4) + 2);
-            const x = ctx.canvas.width / 2;
-            const y = ctx.canvas.height / 2;
 
             selectedImages.forEach((image, idx) => {
                 cleanDraw(
-                  ctx, image, x, y,
+                  ctx, image,
+                  ctx.canvas.width / 2,
+                  ctx.canvas.height / 2,
                   ctx.canvas.width - (ctx.canvas.width / selectedImages.length * idx),
                   ctx.canvas.height - (ctx.canvas.height / selectedImages.length * idx),
                 );
             });
         }
+    },
+    "blend": {
+        name: "Blending",
+        minImages: 2,
+        place: (ctx, images, config) => {
+            const selectedImages = shuffle(images).slice(0, config.numImages || randint(2) + 2);
+            ctx.globalCompositeOperation = choice(["difference", "saturation", "soft-light", "overlay"]);
+            selectedImages.forEach((image) => {
+                cleanDraw(
+                  ctx, image,
+                  ctx.canvas.width / 2, ctx.canvas.height / 2,
+                  ctx.canvas.width, ctx.canvas.height
+                );
+            });
+        }
     }
 };
 

src/components/Collage.vue

@@ -91,10 +91,8 @@ export default class Collage extends Vue {
         return this.lastMode ? this.lastMode.forceConfig || {} : {};
     }
 
-
     private mounted() {
-        const canvas = (this.$refs.canvas as HTMLCanvasElement);
-        this.context = canvas.getContext("2d") as CanvasRenderingContext2D;
+        this.reset();
     }
 
     @Watch("images")
@@ -103,6 +101,7 @@ export default class Collage extends Vue {
     private renderCollage() {
         if (this.images.length >= this.currentMode.minImages) {
             this.lastActiveModeType = this.currentModeType;
+            this.reset();
             this.currentMode.place(this.context, this.images, this.collageConfig);
         }
     }
@@ -113,10 +112,17 @@ export default class Collage extends Vue {
             this.renderCollage();
         });
     }
+
+    private reset() {
+        const canvas = (this.$refs.canvas as HTMLCanvasElement);
+        this.context = canvas.getContext("2d") as CanvasRenderingContext2D;
+        this.context.clearRect(0, 0, canvas.width, canvas.height);
+    }
 }
 </script>
 
 <!-- Add "scoped" attribute to limit CSS to this component only -->
+<!--suppress CssUnusedSymbol -->
 <style scoped>
 .collage {
     margin: 2rem;

src/utils.ts

@@ -17,3 +17,7 @@ export function shuffle<T>(a: T[]): T[] {
 export function randint(n: number) {
     return Math.floor(Math.random() * n);
 }
+
+export function choice<T>(arr: T[]): T {
+    return arr[randint(arr.length)];
+}