It appears that copying a Uint8Array into a Uint8ClampedArray is much slower than cloning the Uint8Array and using its underlying ArrayBuffer:
const foo = new Uint8Array(0x10000000); // 256MiB
console.time('Copy into Uint8ClampedArray');
const bar = new Uint8ClampedArray(foo);
console.timeEnd('Copy into Uint8ClampedArray');The code above clocks at ~160ms on my machine (Chrome v96, MacBook Pro).
const foo = new Uint8Array(0x10000000); // 256MiB
console.time('Clone, then use ArrayBuffer');
const bar = new Uint8ClampedArray(new Uint8Array(foo).buffer);
console.timeEnd('Clone, then use ArrayBuffer');The code above clocks at ~70ms on my machine.
Firefox gives similar stats (140ms vs 60ms), while Safari shows more extreme differences (550ms vs 30ms).
I'm not seeing those time differences in browser or in NodeJs
foo = new Uint8Array(256 * 1024**2); // 256MiB
console.time(label = 'Copy into Uint8ClampedArray');
bar = new Uint8ClampedArray(foo);
console.timeEnd(label);
foo = new Uint8Array(256 * 1024**2); // 256MiB
console.time(label = 'Clone, then use ArrayBuffer');
bar = new Uint8ClampedArray(new Uint8Array(foo).buffer);
console.timeEnd(label);
$ node -v && node test.js
v17.2.0
Copy into Uint8ClampedArray: 174.049ms
Clone, then use ArrayBuffer: 193.819ms
$ node -v && node test.js
v17.2.0
Copy into Uint8ClampedArray: 170.152ms
Clone, then use ArrayBuffer: 192.41ms
$ node -v && node test.js
v17.2.0
Copy into Uint8ClampedArray: 168.555ms
Clone, then use ArrayBuffer: 209.525ms