@danielbiegler/vendure-plugin-blurry-image-lazy-loading
Version:
Generates image hashes for displaying blurry previews when loading images on the frontend.
359 lines (358 loc) • 14.5 kB
JavaScript
"use strict";
/**
* DISCLAIMER:
*
* All the functions inside this file were copied (and slightly modified) on the 2024-12-18 from: https://github.com/evanw/thumbhash
*
* The specific commit including the copied code: https://github.com/evanw/thumbhash/commit/d2e50a74ac26d1e2539c8b6160ea8828b5307de3
*
* Permalinks to the specific file version:
* - https://github.com/evanw/thumbhash/blob/a652ce6ed691242f459f468f0a8756cda3b90a82/js/thumbhash.js
* - https://github.com/evanw/thumbhash/blob/a652ce6ed691242f459f468f0a8756cda3b90a82/js/thumbhash.d.ts
*
* Modifications to the original code include:
* - Typescript type annotations and coercion
* - Code comments
* - Whitespace auto formatting
* - Removed throwing an error for images larger than 100x100px
*
* Now follows the original license and copyright notice at time of copying
*
* ========================================================================================================================================
*
* Copyright (c) 2023 Evan Wallace
*
* Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
Object.defineProperty(exports, "__esModule", { value: true });
exports.thumbHashToDataURL = exports.rgbaToDataURL = exports.thumbHashToApproximateAspectRatio = exports.thumbHashToAverageRGBA = exports.thumbHashToRGBA = exports.rgbaToThumbHash = void 0;
/**
* Encodes an RGBA image to a ThumbHash. RGB should not be premultiplied by A.
*
* @param w The width of the input image.
* @param h The height of the input image.
* @param rgba The pixels in the input image, row-by-row. Must have w*h*4 elements.
* @returns The ThumbHash as a Uint8Array.
*/
function rgbaToThumbHash(w, h, rgba) {
// Note(Dan): removed the following size constraint: Dont tell me what to do, mind your own business
// Leaving the original statement for history sake
// Encoding an image larger than 100x100 is slow with no benefit
// if (w > 100 || h > 100) throw new Error(`${w}x${h} doesn't fit in 100x100`);
let { PI, round, max, cos, abs } = Math;
// Determine the average color
let avg_r = 0, avg_g = 0, avg_b = 0, avg_a = 0;
for (let i = 0, j = 0; i < w * h; i++, j += 4) {
let alpha = rgba[j + 3] / 255;
avg_r += (alpha / 255) * rgba[j];
avg_g += (alpha / 255) * rgba[j + 1];
avg_b += (alpha / 255) * rgba[j + 2];
avg_a += alpha;
}
if (avg_a) {
avg_r /= avg_a;
avg_g /= avg_a;
avg_b /= avg_a;
}
let hasAlpha = avg_a < w * h;
let l_limit = hasAlpha ? 5 : 7; // Use fewer luminance bits if there's alpha
let lx = max(1, round((l_limit * w) / max(w, h)));
let ly = max(1, round((l_limit * h) / max(w, h)));
let l = []; // luminance
let p = []; // yellow - blue
let q = []; // red - green
let a = []; // alpha
// Convert the image from RGBA to LPQA (composite atop the average color)
for (let i = 0, j = 0; i < w * h; i++, j += 4) {
let alpha = rgba[j + 3] / 255;
let r = avg_r * (1 - alpha) + (alpha / 255) * rgba[j];
let g = avg_g * (1 - alpha) + (alpha / 255) * rgba[j + 1];
let b = avg_b * (1 - alpha) + (alpha / 255) * rgba[j + 2];
l[i] = (r + g + b) / 3;
p[i] = (r + g) / 2 - b;
q[i] = r - g;
a[i] = alpha;
}
// Encode using the DCT into DC (constant) and normalized AC (varying) terms
let encodeChannel = (channel, nx, ny) => {
let dc = 0, ac = [], scale = 0, fx = [];
for (let cy = 0; cy < ny; cy++) {
for (let cx = 0; cx * ny < nx * (ny - cy); cx++) {
let f = 0;
for (let x = 0; x < w; x++)
fx[x] = cos((PI / w) * cx * (x + 0.5));
for (let y = 0; y < h; y++)
for (let x = 0, fy = cos((PI / h) * cy * (y + 0.5)); x < w; x++)
f += channel[x + y * w] * fx[x] * fy;
f /= w * h;
if (cx || cy) {
ac.push(f);
scale = max(scale, abs(f));
}
else {
dc = f;
}
}
}
if (scale)
for (let i = 0; i < ac.length; i++)
ac[i] = 0.5 + (0.5 / scale) * ac[i];
return [dc, ac, scale];
};
let [l_dc, l_ac, l_scale] = encodeChannel(l, max(3, lx), max(3, ly));
let [p_dc, p_ac, p_scale] = encodeChannel(p, 3, 3);
let [q_dc, q_ac, q_scale] = encodeChannel(q, 3, 3);
let [a_dc, a_ac, a_scale] = hasAlpha ? encodeChannel(a, 5, 5) : [];
// Write the constants
let isLandscape = w > h;
let header24 = round(63 * l_dc) |
(round(31.5 + 31.5 * p_dc) << 6) |
(round(31.5 + 31.5 * q_dc) << 12) |
(round(31 * l_scale) << 18) |
(hasAlpha << 23);
let header16 = (isLandscape ? ly : lx) |
(round(63 * p_scale) << 3) |
(round(63 * q_scale) << 9) |
(isLandscape << 15);
let hash = [header24 & 255, (header24 >> 8) & 255, header24 >> 16, header16 & 255, header16 >> 8];
let ac_start = hasAlpha ? 6 : 5;
let ac_index = 0;
// We know these will be defined if `hasAlpha` is `true`, see definition above
if (hasAlpha)
hash.push(round(15 * a_dc) | (round(15 * a_scale) << 4));
// Write the varying factors
for (let ac of hasAlpha ? [l_ac, p_ac, q_ac, a_ac] : [l_ac, p_ac, q_ac])
for (let f of ac)
hash[ac_start + (ac_index >> 1)] |= round(15 * f) << ((ac_index++ & 1) << 2);
return new Uint8Array(hash);
}
exports.rgbaToThumbHash = rgbaToThumbHash;
/**
* Decodes a ThumbHash to an RGBA image. RGB is not be premultiplied by A.
*
* @param hash The bytes of the ThumbHash.
* @returns The width, height, and pixels of the rendered placeholder image.
*/
function thumbHashToRGBA(hash) {
let { PI, min, max, cos, round } = Math;
// Read the constants
let header24 = hash[0] | (hash[1] << 8) | (hash[2] << 16);
let header16 = hash[3] | (hash[4] << 8);
let l_dc = (header24 & 63) / 63;
let p_dc = ((header24 >> 6) & 63) / 31.5 - 1;
let q_dc = ((header24 >> 12) & 63) / 31.5 - 1;
let l_scale = ((header24 >> 18) & 31) / 31;
let hasAlpha = header24 >> 23;
let p_scale = ((header16 >> 3) & 63) / 63;
let q_scale = ((header16 >> 9) & 63) / 63;
let isLandscape = header16 >> 15;
let lx = max(3, isLandscape ? (hasAlpha ? 5 : 7) : header16 & 7);
let ly = max(3, isLandscape ? header16 & 7 : hasAlpha ? 5 : 7);
let a_dc = hasAlpha ? (hash[5] & 15) / 15 : 1;
let a_scale = (hash[5] >> 4) / 15;
// Read the varying factors (boost saturation by 1.25x to compensate for quantization)
let ac_start = hasAlpha ? 6 : 5;
let ac_index = 0;
let decodeChannel = (nx, ny, scale) => {
let ac = [];
for (let cy = 0; cy < ny; cy++)
for (let cx = cy ? 0 : 1; cx * ny < nx * (ny - cy); cx++)
ac.push((((hash[ac_start + (ac_index >> 1)] >> ((ac_index++ & 1) << 2)) & 15) / 7.5 - 1) * scale);
return ac;
};
let l_ac = decodeChannel(lx, ly, l_scale);
let p_ac = decodeChannel(3, 3, p_scale * 1.25);
let q_ac = decodeChannel(3, 3, q_scale * 1.25);
let a_ac = hasAlpha && decodeChannel(5, 5, a_scale);
// Decode using the DCT into RGB
let ratio = thumbHashToApproximateAspectRatio(hash);
let w = round(ratio > 1 ? 32 : 32 * ratio);
let h = round(ratio > 1 ? 32 / ratio : 32);
let rgba = new Uint8Array(w * h * 4), fx = [], fy = [];
for (let y = 0, i = 0; y < h; y++) {
for (let x = 0; x < w; x++, i += 4) {
let l = l_dc, p = p_dc, q = q_dc, a = a_dc;
// Precompute the coefficients
for (let cx = 0, n = max(lx, hasAlpha ? 5 : 3); cx < n; cx++)
fx[cx] = cos((PI / w) * (x + 0.5) * cx);
for (let cy = 0, n = max(ly, hasAlpha ? 5 : 3); cy < n; cy++)
fy[cy] = cos((PI / h) * (y + 0.5) * cy);
// Decode L
for (let cy = 0, j = 0; cy < ly; cy++)
for (let cx = cy ? 0 : 1, fy2 = fy[cy] * 2; cx * ly < lx * (ly - cy); cx++, j++)
l += l_ac[j] * fx[cx] * fy2;
// Decode P and Q
for (let cy = 0, j = 0; cy < 3; cy++) {
for (let cx = cy ? 0 : 1, fy2 = fy[cy] * 2; cx < 3 - cy; cx++, j++) {
let f = fx[cx] * fy2;
p += p_ac[j] * f;
q += q_ac[j] * f;
}
}
// Decode A
if (hasAlpha)
for (let cy = 0, j = 0; cy < 5; cy++)
for (let cx = cy ? 0 : 1, fy2 = fy[cy] * 2; cx < 5 - cy; cx++, j++)
// We know `a_ac` is an array because of the `hasAlpha` check, see definition above
a += a_ac[j] * fx[cx] * fy2;
// Convert to RGB
let b = l - (2 / 3) * p;
let r = (3 * l - b + q) / 2;
let g = r - q;
rgba[i] = max(0, 255 * min(1, r));
rgba[i + 1] = max(0, 255 * min(1, g));
rgba[i + 2] = max(0, 255 * min(1, b));
rgba[i + 3] = max(0, 255 * min(1, a));
}
}
return { w, h, rgba };
}
exports.thumbHashToRGBA = thumbHashToRGBA;
/**
* Extracts the average color from a ThumbHash. RGB is not be premultiplied by A.
*
* @param hash The bytes of the ThumbHash.
* @returns The RGBA values for the average color. Each value ranges from 0 to 1.
*/
function thumbHashToAverageRGBA(hash) {
let { min, max } = Math;
let header = hash[0] | (hash[1] << 8) | (hash[2] << 16);
let l = (header & 63) / 63;
let p = ((header >> 6) & 63) / 31.5 - 1;
let q = ((header >> 12) & 63) / 31.5 - 1;
let hasAlpha = header >> 23;
let a = hasAlpha ? (hash[5] & 15) / 15 : 1;
let b = l - (2 / 3) * p;
let r = (3 * l - b + q) / 2;
let g = r - q;
return {
r: max(0, min(1, r)),
g: max(0, min(1, g)),
b: max(0, min(1, b)),
a,
};
}
exports.thumbHashToAverageRGBA = thumbHashToAverageRGBA;
/**
* Extracts the approximate aspect ratio of the original image.
*
* @param hash The bytes of the ThumbHash.
* @returns The approximate aspect ratio (i.e. width / height).
*/
function thumbHashToApproximateAspectRatio(hash) {
let header = hash[3];
let hasAlpha = hash[2] & 0x80;
let isLandscape = hash[4] & 0x80;
let lx = isLandscape ? (hasAlpha ? 5 : 7) : header & 7;
let ly = isLandscape ? header & 7 : hasAlpha ? 5 : 7;
return lx / ly;
}
exports.thumbHashToApproximateAspectRatio = thumbHashToApproximateAspectRatio;
/**
* Encodes an RGBA image to a PNG data URL. RGB should not be premultiplied by
* A. This is optimized for speed and simplicity and does not optimize for size
* at all. This doesn't do any compression (all values are stored uncompressed).
*
* @param w The width of the input image.
* @param h The height of the input image.
* @param rgba The pixels in the input image, row-by-row. Must have w*h*4 elements.
* @returns A data URL containing a PNG for the input image.
*/
function rgbaToDataURL(w, h, rgba) {
let row = w * 4 + 1;
let idat = 6 + h * (5 + row);
let bytes = [
137,
80,
78,
71,
13,
10,
26,
10,
0,
0,
0,
13,
73,
72,
68,
82,
0,
0,
w >> 8,
w & 255,
0,
0,
h >> 8,
h & 255,
8,
6,
0,
0,
0,
0,
0,
0,
0,
idat >>> 24,
(idat >> 16) & 255,
(idat >> 8) & 255,
idat & 255,
73,
68,
65,
84,
120,
1,
];
let table = [
0, 498536548, 997073096, 651767980, 1994146192, 1802195444, 1303535960, 1342533948, -306674912, -267414716,
-690576408, -882789492, -1687895376, -2032938284, -1609899400, -1111625188,
];
let a = 1, b = 0;
for (let y = 0, i = 0, end = row - 1; y < h; y++, end += row - 1) {
bytes.push(y + 1 < h ? 0 : 1, row & 255, row >> 8, ~row & 255, (row >> 8) ^ 255, 0);
for (b = (b + a) % 65521; i < end; i++) {
let u = rgba[i] & 255;
bytes.push(u);
a = (a + u) % 65521;
b = (b + a) % 65521;
}
}
bytes.push(b >> 8, b & 255, a >> 8, a & 255, 0, 0, 0, 0, 0, 0, 0, 0, 73, 69, 78, 68, 174, 66, 96, 130);
for (let [start, end] of [
[12, 29],
[37, 41 + idat],
]) {
let c = ~0;
for (let i = start; i < end; i++) {
c ^= bytes[i];
c = (c >>> 4) ^ table[c & 15];
c = (c >>> 4) ^ table[c & 15];
}
c = ~c;
bytes[end++] = c >>> 24;
bytes[end++] = (c >> 16) & 255;
bytes[end++] = (c >> 8) & 255;
bytes[end++] = c & 255;
}
return "data:image/png;base64," + btoa(String.fromCharCode(...bytes));
}
exports.rgbaToDataURL = rgbaToDataURL;
/**
* Decodes a ThumbHash to a PNG data URL. This is a convenience function that
* just calls "thumbHashToRGBA" followed by "rgbaToDataURL".
*
* @param hash The bytes of the ThumbHash.
* @returns A data URL containing a PNG for the rendered ThumbHash.
*/
function thumbHashToDataURL(hash) {
let image = thumbHashToRGBA(hash);
return rgbaToDataURL(image.w, image.h, image.rgba);
}
exports.thumbHashToDataURL = thumbHashToDataURL;