feat: convert image if needed when encoding (#466)

And do not allow to convert bit depth of image to 1 because only Mask are supposed to have this bit depth

Author: EscapedGibbon

src/operations/__tests__/convertBitDepth.test.ts

@@ -65,3 +65,13 @@ test('throw if converting to same bit depth', () => {
     img.convertBitDepth(8);
   }).toThrow('cannot convert image to same bitDepth');
 });
+test('throw if converting to unsupported bit depth', () => {
+  const img = testUtils.createRgbaImage([
+    [256, 256, 256, 256, 512, 512, 512, 512],
+    [768, 768, 768, 768, 1024, 1024, 1024, 1024],
+  ]);
+
+  expect(() => {
+    img.convertBitDepth(1);
+  }).toThrow('This image bit depth is not supported: 1');
+});

src/operations/convertBitDepth.ts

@@ -13,8 +13,12 @@ export function convertBitDepth(image: Image, newBitDepth: BitDepth): Image {
 
   if (newBitDepth === 16) {
     return convertToUint16(image);
-  } else {
+  } else if (newBitDepth === 8) {
     return convertToUint8(image);
+  } else {
+    throw new RangeError(
+      `This image bit depth is not supported: ${newBitDepth}`,
+    );
   }
 }
 

src/save/__tests__/encodeBmp.test.ts

@@ -35,3 +35,13 @@ test('encode 10x2 mask', () => {
   const buffer = encodeBmp(mask).buffer;
   expect(buffer).toEqual(result.buffer);
 });
+test('should throw error', () => {
+  const image = testUtils.createGreyImage([
+    [255, 255, 255, 0, 0, 255, 0, 255, 0, 255],
+    [255, 0, 255, 0, 255, 0, 0, 255, 255, 255],
+  ]);
+
+  expect(() => encodeBmp(image)).toThrow(
+    'Image bmp encoding is not implemented.',
+  );
+});

src/save/__tests__/encodePng.test.ts

@@ -17,3 +17,11 @@ test('should encode a 16bits image correctly', () => {
   expect(imgDup.bitDepth).toBe(16);
   expect(imgDup).toMatchImage(img);
 });
+
+test('add mask test', () => {
+  const img = testUtils.load('formats/tif/grey16.tif');
+  const mask = img.threshold();
+  const imgDup = decode(encodePng(mask));
+  expect(imgDup.colorModel).toBe('GREY');
+  expect(imgDup.bitDepth).toBe(8);
+});

src/save/encodeBmp.ts

@@ -9,7 +9,7 @@ import { Mask } from '../Mask';
  * @param mask - The mask instance.
  * @returns The buffer.
  */
-export function encodeBmp(mask: Mask | Image) {
+export function encodeBmp(mask: Image | Mask) {
   if (!(mask instanceof Mask)) {
     throw new TypeError('Image bmp encoding is not implemented.');
   }

src/save/encodeJpeg.ts

@@ -22,10 +22,7 @@ export function encodeJpeg(
   options: EncodeJpegOptions = {},
 ): Uint8Array {
   const { quality = 50 } = options;
-  if (!(image instanceof Image)) {
-    throw new TypeError('Mask JPG/JPEG encoding is not supported.');
-  }
-  if (image.colorModel !== 'RGBA') {
+  if (image.colorModel !== 'RGBA' || image instanceof Mask) {
     image = image.convertColor('RGBA');
   }
   if (image.bitDepth !== 8) {

src/save/encodePng.ts

@@ -15,17 +15,12 @@ export function encodePng(
   image: Image | Mask,
   options?: EncodePngOptions,
 ): Uint8Array {
-  if (!(image instanceof Image)) {
-    throw new TypeError('Mask PNG encoding is not supported.');
-  }
-  if (image.bitDepth !== 8 && image.bitDepth !== 16) {
-    image = image.convertBitDepth(8);
-  }
   if (
-    image.colorModel !== 'RGB' &&
-    image.colorModel !== 'RGBA' &&
-    image.colorModel !== 'GREY' &&
-    image.colorModel !== 'GREYA'
+    (image.colorModel !== 'RGB' &&
+      image.colorModel !== 'RGBA' &&
+      image.colorModel !== 'GREY' &&
+      image.colorModel !== 'GREYA') ||
+    image instanceof Mask
   ) {
     image = image.convertColor('GREY');
   }

src/save/write.ts

@@ -137,12 +137,12 @@ function getDataToWrite(
 ): Uint8Array {
   if (!options || !('format' in options)) {
     const extension = nodePath.extname(destinationPath).slice(1).toLowerCase();
-    if (extension === 'png' || extension === 'jpg' || extension === 'jpeg') {
-      if (image instanceof Mask) {
-        image = image.convertColor('GREY');
-      }
-      return encode(image, { ...options, format: extension });
-    } else if (extension === 'bmp') {
+    if (
+      extension === 'png' ||
+      extension === 'jpg' ||
+      extension === 'jpeg' ||
+      extension === 'bmp'
+    ) {
       return encode(image, { ...options, format: extension });
     } else {
       throw new RangeError(