png-dpi-reader-writer

https://gyazo.com/2d891b066047606652f45104aaec5f2b https://github.com/daiiz/deno-png-dpi-reader-writer

Motivation

CLI Examples

code:mod.ts

code:share.ts

import {Buffer} from 'deno'

export interface ImageInfo {

width?: number,

height?: number,

dpi?: number

}

export const toDec = (arr: Uint8Array): number => {

const _toBin = (value, bits) => value.toString(2).padStart(bits, '0')

return parseInt(Array.from(arr).map(v => _toBin(v, 8)).join(''), 2)

}

export async function isPng (buf: Buffer): Promise<boolean> {

const pngSignature = '137 80 78 71 13 10 26 10'

const p = new Uint8Array(8); await buf.read(p)

return p.join(' ').toUpperCase() === pngSignature

}

export async function readIHDR (buf: Buffer): Promise<ImageInfo> {

// Length, ChunkType

await skip(buf, 4 + 4)

const width = new Uint8Array(4); await buf.read(width)

const height = new Uint8Array(4); await buf.read(height)

// Bit depth, Color type, Compression method, Filter method, nterlace method, CRC

await skip(buf, 1 + 1 + 1 + 1 + 1 + 4)

return {

width: toDec(width),

height: toDec(height)

}

}

export function getCharCodes (raw: string): string {

return raw.split('').map(c => c.charCodeAt(0)).join(' ')

}

export async function skip (buf: Buffer, bytes: number) {

const _ = new Uint8Array(bytes);

await buf.read(_)

}