fix: undo breaking change: alpha can be 0 or 1 again

Author: targos

src/PNGEncoder.ts

@@ -140,16 +140,22 @@ function checkInteger(value: number, name: string): number {
 function getColourType(
   data: IImageData
 ): { channels: number; bitDepth: number; colourType: number } {
-  const { channels = 4, alpha = true, bitDepth = 8 } = data;
+  const { channels = 4, bitDepth = 8 } = data;
   if (channels !== 4 && channels !== 3 && channels !== 2 && channels !== 1) {
     throw new RangeError(`unsupported number of channels: ${channels}`);
   }
   if (bitDepth !== 8 && bitDepth !== 16) {
     throw new RangeError(`unsupported bit depth: ${bitDepth}`);
   }
+
+  let { alpha = true } = data;
+  if (alpha === 0 || alpha === 1) {
+    alpha = Boolean(alpha);
+  }
   if (typeof alpha !== 'boolean') {
     throw new TypeError(`unsupported alpha: ${alpha}`);
   }
+
   const returnValue = { channels, bitDepth, colourType: -1 };
   switch (channels) {
     case 4:

src/types.ts

@@ -32,7 +32,7 @@ export interface IImageData {
   height: number;
   data: PNGDataArray;
   channels?: number;
-  alpha?: boolean;
+  alpha?: boolean | 0 | 1;
   bitDepth?: number;
 }