Utility function

shockpkg · Sep 25, 2023 · ed2803d · ed2803d
1 parent b9ef636
commit ed2803d
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Showing 2 changed files with 51 additions and 36 deletions.
diff --git a/src/icon.ts b/src/icon.ts
@@ -1,7 +1,7 @@
 import {PNG} from 'pngjs';
 
 import {IImageData} from './types';
-import {concatUint8Arrays, pngReader, pngEncode} from './util';
+import {concatUint8Arrays, pngRepack} from './util';
 
 /**
  * Icon object.
@@ -69,40 +69,7 @@ export abstract class Icon {
 			png.on('end', resolve);
 			png.pack();
 		});
-		let ihdr: Uint8Array | null = null;
-		let iend: Uint8Array | null = null;
-		const idats = [];
-		for (const [tag, data] of pngReader(concatUint8Arrays(packed))) {
-			switch (tag) {
-				// IDAT
-				case 0x49444154: {
-					idats.push(data);
-					break;
-				}
-				// IHDR
-				case 0x49484452: {
-					ihdr = data;
-					break;
-				}
-				// IEND
-				case 0x49454e44: {
-					iend = data;
-					break;
-				}
-				default: {
-					// Discard others.
-				}
-			}
-		}
-		if (!ihdr || !iend) {
-			throw new Error('Encode error');
-		}
-		const pieces: [number, Uint8Array][] = [[0x49484452, ihdr]];
-		if (srgb !== null) {
-			pieces.push([0x73524742, new Uint8Array([srgb])]);
-		}
-		pieces.push([0x49444154, concatUint8Arrays(idats)], [0x49454e44, iend]);
-		return pngEncode(pieces);
+		return pngRepack(concatUint8Arrays(packed));
 	}
 
 	/**

diff --git a/src/util.ts b/src/util.ts
@@ -2,6 +2,10 @@ import {IPngIhdr} from './types';
 
 const PNG_MAGIC = [137, 80, 78, 71, 13, 10, 26, 10];
 const PNG_MAGIC_SIZE = 8;
+const IHDR = 0x49484452;
+const SRGB = 0x73524742;
+const IDAT = 0x49444154;
+const IEND = 0x49454e44;
 
 const CRC32_TABLE: number[] = [];
 
@@ -110,6 +114,50 @@ export function pngEncode(tags: Readonly<[number, Readonly<Uint8Array>][]>) {
 	return r;
 }
 
+/**
+ * Repack PNG tag data with a single IDAT.
+ *
+ * @param data PNG data.
+ * @param srgb Set an SRGB value.
+ * @returns PNG data.
+ */
+export function pngRepack(
+	data: Readonly<Uint8Array>,
+	srgb: number | null = null
+) {
+	let ihdr: Uint8Array | null = null;
+	let iend: Uint8Array | null = null;
+	const idats = [];
+	for (const [tag, d] of pngReader(data)) {
+		switch (tag) {
+			case IDAT: {
+				idats.push(d);
+				break;
+			}
+			case IHDR: {
+				ihdr = d;
+				break;
+			}
+			case IEND: {
+				iend = d;
+				break;
+			}
+			default: {
+				// Discard others.
+			}
+		}
+	}
+	if (!ihdr || !iend) {
+		throw new Error('Invalid PNG');
+	}
+	const pieces: [number, Uint8Array][] = [[IHDR, ihdr]];
+	if (srgb !== null) {
+		pieces.push([SRGB, new Uint8Array([srgb])]);
+	}
+	pieces.push([IDAT, concatUint8Arrays(idats)], [IEND, iend]);
+	return pngEncode(pieces);
+}
+
 /**
  * Read PNG IHDR data.
  *
@@ -118,7 +166,7 @@ export function pngEncode(tags: Readonly<[number, Readonly<Uint8Array>][]>) {
  */
 export function pngIhdr(data: Readonly<Uint8Array>): IPngIhdr {
 	for (const [tag, td] of pngReader(data)) {
-		if (tag === 0x49484452) {
+		if (tag === IHDR) {
 			const d = new DataView(td.buffer, td.byteOffset, td.byteLength);
 			return {
 				width: d.getUint32(0, false),