Added trimBounds to MagickImageCollection.

Author: dlemstra

src/magick-image-collection.ts

@@ -346,6 +346,13 @@ export interface IMagickImageCollection extends Array<IMagickImage>, IDisposable
      */
     smushVertical<TReturnType>(offset: number, func: AsyncImageCallback<TReturnType>): Promise<TReturnType>;
 
+    /**
+     * Determine the overall bounds of all the image layers just as in {@link MagickImageCollection#merge},
+     * then adjust the the canvas and offsets to be relative to those bounds,
+     * without overlaying the images.
+     */
+    trimBounds(): void;
+
     /**
      * Write all image frames to a byte array.
      * @param func The function to execute with the byte array.
@@ -645,6 +652,10 @@ export class MagickImageCollection extends Array<MagickImage> implements IMagick
         return this.smush(offset, true, func);
     }
 
+    trimBounds(): void {
+        this.mergeImages(LayerMethod.Trimbounds, () => { /* special case where the returned image is null */ });
+    }
+
     write<TReturnType>(func: (data: Uint8Array) => TReturnType): TReturnType;
     write<TReturnType>(format: MagickFormat, func: (data: Uint8Array) => TReturnType): TReturnType;
     write<TReturnType>(func: (data: Uint8Array) => Promise<TReturnType>): Promise<TReturnType>;

tests/magick-image-collection/trim-bounds.spec.ts

@@ -0,0 +1,32 @@
+/*
+  Copyright Dirk Lemstra https://github.com/dlemstra/magick-wasm.
+  Licensed under the Apache License, Version 2.0.
+*/
+
+import { MagickColors } from '@src/magick-colors';
+import { MagickImage } from '@src/magick-image';
+import { TestImages } from '@test/test-images';
+
+describe('MagickImageCollection#trimBounds', () => {
+    it('should throw exception when collection is empty', () => {
+        TestImages.emptyCollection.use((images) => {
+            expect(() => {
+                images.trimBounds();
+            }).toThrowError('operation requires at least one image');
+        });
+    });
+
+    it('should adjust the canvas', () => {
+        TestImages.emptyCollection.use(images => {
+
+            images.push(MagickImage.create(MagickColors.Red, 6, 7));
+            images.push(MagickImage.create(MagickColors.Red, 8, 5));
+
+            images.trimBounds();
+
+            expect(images.length).toBe(2);
+            expect(images[0].page.toString()).toBe('8x7+0+0');
+            expect(images[1].page.toString()).toBe('8x7+0+0');
+        });
+    });
+});