JPEG

JPEG Encoder/Decoder for Deno based on Node's jpeg-js.

Example

Decode JPEG

import JPEG from "https://deno.land/x/jpeg/mod.ts";

const img = await Deno.readFile("./img.jpg");
const raw = JPEG.decode(img);

console.log(raw);

/*
{
  width: 850,
  height: 571,
  exifBuffer: undefined,
  data: Buffer(1941400) [
     78,  73,  83, 255,  86,  81,  91, 255,  82,  77,  85, 255,  68,  63,  71,
    255,  61,  56,  64, 255,  67,  62,  70, 255,  73,  68,  76, 255,  71,  66,
     74, 255,  65,  60,  66, 255,  75,  70,  76, 255,  83,  78,  84, 255,  81,
     76,  82, 255,  75,  71,  74, 255,  79,  75,  78, 255,  96,  92,  95, 255,
    113, 109, 112, 255,  95,  92,  99, 255,  86,  83,  90, 255,  89,  86,  93,
    255,  91,  88,  95, 255,  74,  71,  78, 255,  57,  54,  61, 255,  65,  62,
     69, 255,  83,  80,  87, 255,  83,  80,  87, 255,
    ... 1941300 more items
  ]
}
*/

Encoding JPEG

import JPEG from "https://deno.land/x/jpeg/mod.ts";

const width = 320, height = 180;
const frameData = new Uint8Array(width * height * 4);

let i = 0;
while(i < frameData.length) {
    frameData[i++] = 255; // red
    frameData[i++] = 66; // green
    frameData[i++] = 159; // blue
    frameData[i++] = 0; // alpha - ignored in JPEGs
}

const rawImageData = {
    data: frameData,
    width: width,
    height: height,
};
var jpegImageData = JPEG.encode(rawImageData, 50);
console.log(jpegImageData);

Deno.writeFileSync("./test/enc.jpg", jpegImageData.data);

/*
{
  data: Uint8Array(2222) [
    255, 216, 255, 224,  0,  16,  74,  70,  73,  70,   0,   1,   1,  0,  0,
      1,   0,   1,   0,  0, 255, 219,   0, 132,   0,  16,  11,  12, 14, 12,
     10,  16,  14,  13, 14,  18,  17,  16,  19,  24,  40,  26,  24, 22, 22,
     24,  49,  35,  37, 29,  40,  58,  51,  61,  60,  57,  51,  56, 55, 64,
     72,  92,  78,  64, 68,  87,  69,  55,  56,  80, 109,  81,  87, 95, 98,
    103, 104, 103,  62, 77, 113, 121, 112, 100, 120,  92, 101, 103, 99,  1,
     17,  18,  18,  24, 21,  24,  47,  26,  26,  47,
    ... 2122 more items
  ],
  width: 320,
  height: 180
}
*/

Options

Decode Options

Option	Description	Default
colorTransform	Transform alternate colorspaces like YCbCr. undefined means respect the default behavior encoded in metadata.	undefined
useTArray	Decode pixels into a typed Uint8Array instead of a Buffer.	false
formatAsRGBA	Decode pixels into RGBA vs. RGB.	true
tolerantDecoding	Be more tolerant when encountering technically invalid JPEGs.	true
maxResolutionInMP	The maximum resolution image that jpeg should attempt to decode in megapixels. Images larger than this resolution will throw an error instead of decoding.	100
maxMemoryUsageInMB	The (approximate) maximum memory that jpeg should allocate while attempting to decode the image in mebibyte. Images requiring more memory than this will throw an error instead of decoding.	512