fix: remove misleading kind option

Replaced by separate "components" and "alpha" options.

BREAKING CHANGE:

The "kind" option was misleading and has been replaced by separate
"components" and "alpha" options.

Author: targos

README.md

@@ -34,7 +34,8 @@ __Arguments__
   * `height` - The height of the image
   * `data` - An array or TypedArray with the image data
   * `bitDepth` - A number indicating the bit depth (only 8 and 16 are supported now). Defaults to 8.
-  * `kind` - One of `'RGBA'`, `'RGB'`, `'GREYA'`, `'GREY'`. This will determine the number of channels and the colour type of the image. Defaults to `'RGBA'`.
+  * `components` - Number of non-alpha channels (1 or 3 are supported). Defaults to 3.
+  * `alpha` - Boolean indicating if an alpha channel is present. Defaults to true.
 
 ## PNG standard
 

__tests__/encode.js

@@ -30,7 +30,8 @@ describe('encode', () => {
             width: 2,
             height: 3,
             data: dataArray,
-            kind: 'GREY'
+            components: 1,
+            alpha: false
         });
         expect(data).toBeInstanceOf(Uint8Array);
         const decoded = decode(data);
@@ -53,7 +54,8 @@ describe('encode', () => {
             height: 2,
             bitDepth: 16,
             data: dataArray,
-            kind: 'RGB'
+            components: 3,
+            alpha: false
         });
         expect(data).toBeInstanceOf(Uint8Array);
         const decoded = decode(data);
@@ -68,6 +70,17 @@ describe('encode', () => {
         expect(decoded.data).toBeInstanceOf(Uint16Array);
         expect(decoded.data).toEqual(dataArray);
     });
+
+    it('errors', () => {
+        expect(() => encode({width: 1, height: 1, bitDepth: 8, data: [], components: 2, alpha: true}))
+            .toThrow('unsupported number of components: 2');
+        expect(() => encode({width: 1, height: 1, bitDepth: 8, data: [], components: 3, alpha: 2}))
+            .toThrow('unsupported number of channels: 5');
+        expect(() => encode({width: 1.1, height: 1, bitDepth: 8, data: [], components: 3, alpha: false}))
+            .toThrow('width must be a positive integer');
+        expect(() => encode({width: 1, height: undefined, bitDepth: 8, data: [], components: 3, alpha: false}))
+            .toThrow('height must be a positive integer');
+    });
 });
 
 function check(img, values) {

src/PNGEncoder.js

@@ -89,7 +89,7 @@ export default class PNGDecoder extends IOBuffer {
             height: checkInteger(data.height, 'height'),
             data: data.data
         };
-        const {colourType, channels} = getColourType(data.kind);
+        const {colourType, channels} = getColourType(data);
         this._png.colourType = colourType;
         this._png.channels = channels;
         this._png.bitDepth = data.bitDepth || 8;
@@ -111,18 +111,26 @@ function checkInteger(value, name) {
     throw new TypeError(`${name} must be a positive integer`);
 }
 
-function getColourType(kind = 'RGBA') {
-    switch (kind) {
-        case 'RGBA':
+function getColourType(data) {
+    const {
+        components = 3,
+        alpha = true
+    } = data;
+    if (components !== 3 && components !== 1) {
+        throw new RangeError(`unsupported number of components: ${components}`);
+    }
+    const channels = components + Number(alpha);
+    switch (channels) {
+        case 4:
             return {colourType: 6, channels: 4};
-        case 'RGB':
+        case 3:
             return {colourType: 2, channels: 3};
-        case 'GREY':
+        case 1:
             return {colourType: 0, channels: 1};
-        case 'GREYA':
+        case 2:
             return {colourType: 4, channels: 2};
         default:
-            throw new Error(`unknown kind: ${kind}`);
+            throw new Error(`unsupported number of channels: ${channels}`);
     }
 }