const PNG_SIGNATURE = Buffer.from([0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a]); export const WINDOWS_ICON_SIZES = [16, 24, 32, 48, 64, 128, 256] as const; export interface PngIconImage { readonly size: number; readonly contents: Buffer;} export function readPngDimensions(contents: Buffer): { readonly width: number; readonly height: number;} { if ( contents.length < 24 || !contents.subarray(0, PNG_SIGNATURE.length).equals(PNG_SIGNATURE) || contents.toString("ascii", 12, 16) !== "IHDR" ) { throw new Error("Icon Composer produced an invalid PNG."); } return { width: contents.readUInt32BE(16), height: contents.readUInt32BE(20), };} /** Encodes PNG renditions directly into a modern, multi-resolution ICO file. */export function encodePngIco(images: ReadonlyArray<PngIconImage>): Buffer { if (images.length === 0) { throw new Error("An ICO file requires at least one PNG rendition."); } const seenSizes = new Set<number>(); for (const image of images) { if (!Number.isInteger(image.size) || image.size < 1 || image.size > 256) { throw new Error(`ICO rendition size must be an integer from 1 to 256, got ${image.size}.`); } if (seenSizes.has(image.size)) { throw new Error(`ICO rendition size ${image.size} was provided more than once.`); } if (image.contents.length === 0) { throw new Error(`ICO rendition ${image.size}x${image.size} is empty.`); } seenSizes.add(image.size); } const headerSize = 6; const directoryEntrySize = 16; const directorySize = directoryEntrySize * images.length; const header = Buffer.alloc(headerSize + directorySize); header.writeUInt16LE(0, 0); header.writeUInt16LE(1, 2); header.writeUInt16LE(images.length, 4); let imageOffset = header.length; images.forEach((image, index) => { const entryOffset = headerSize + index * directoryEntrySize; const encodedSize = image.size === 256 ? 0 : image.size; header.writeUInt8(encodedSize, entryOffset); header.writeUInt8(encodedSize, entryOffset + 1); header.writeUInt8(0, entryOffset + 2); header.writeUInt8(0, entryOffset + 3); header.writeUInt16LE(1, entryOffset + 4); header.writeUInt16LE(32, entryOffset + 6); header.writeUInt32LE(image.contents.length, entryOffset + 8); header.writeUInt32LE(imageOffset, entryOffset + 12); imageOffset += image.contents.length; }); return Buffer.concat([header, ...images.map((image) => image.contents)]);}
const PNG_SIGNATURE = Buffer.from([0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a]);
export const WINDOWS_ICON_SIZES = [16, 24, 32, 48, 64, 128, 256] as const;
export interface PngIconImage {
readonly size: number;
readonly contents: Buffer;
}
export function readPngDimensions(contents: Buffer): {
readonly width: number;
readonly height: number;
} {
if (
contents.length < 24 ||
!contents.subarray(0, PNG_SIGNATURE.length).equals(PNG_SIGNATURE) ||
contents.toString("ascii", 12, 16) !== "IHDR"
) {
throw new Error("Icon Composer produced an invalid PNG.");
}
return {
width: contents.readUInt32BE(16),
height: contents.readUInt32BE(20),
};
}
/** Encodes PNG renditions directly into a modern, multi-resolution ICO file. */
export function encodePngIco(images: ReadonlyArray<PngIconImage>): Buffer {
if (images.length === 0) {
throw new Error("An ICO file requires at least one PNG rendition.");
}
const seenSizes = new Set<number>();
for (const image of images) {
if (!Number.isInteger(image.size) || image.size < 1 || image.size > 256) {
throw new Error(`ICO rendition size must be an integer from 1 to 256, got ${image.size}.`);
}
if (seenSizes.has(image.size)) {
throw new Error(`ICO rendition size ${image.size} was provided more than once.`);
}
if (image.contents.length === 0) {
throw new Error(`ICO rendition ${image.size}x${image.size} is empty.`);
}
seenSizes.add(image.size);
}
const headerSize = 6;
const directoryEntrySize = 16;
const directorySize = directoryEntrySize * images.length;
const header = Buffer.alloc(headerSize + directorySize);
header.writeUInt16LE(0, 0);
header.writeUInt16LE(1, 2);
header.writeUInt16LE(images.length, 4);
let imageOffset = header.length;
images.forEach((image, index) => {
const entryOffset = headerSize + index * directoryEntrySize;
const encodedSize = image.size === 256 ? 0 : image.size;
header.writeUInt8(encodedSize, entryOffset);
header.writeUInt8(encodedSize, entryOffset + 1);
header.writeUInt8(0, entryOffset + 2);
header.writeUInt8(0, entryOffset + 3);
header.writeUInt16LE(1, entryOffset + 4);
header.writeUInt16LE(32, entryOffset + 6);
header.writeUInt32LE(image.contents.length, entryOffset + 8);
header.writeUInt32LE(imageOffset, entryOffset + 12);
imageOffset += image.contents.length;
});
return Buffer.concat([header, ...images.map((image) => image.contents)]);
}