1663214 - can't get 16-bit data using WebGL2 getPixels

Status: RESOLVED FIXED

(Core :: Graphics: CanvasWebGL, defect)

Description

[ashley_c_mort]

Attachment: ffChrome.PNG

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Firefox/78.0

Steps to reproduce:

We have a 16-bit per channel image editor that runs on WebGL2. We create a 16-bit texImage2D then read the data back out as 16-bit. This works on Chrome but gives an error on Firefox.
WebGL warning: readPixels: Incompatible format or type.

Here is an example. Check the browser console logs when it runs. Chroms will return an array of 16-bit values which is what we'd expect and Firefox will return all 0.

This is the smallest example I could make. In our app we are actually making texImage2D as:
R16UI, RED_INTEGER, UNSIGNED_SHORT
or
RGB16UI, RGB_INTEGER, UNSIGNED_SHORT

and getPixel:
RGBA, UNSIGNED_SHORT

https://jsfiddle.net/mortac8/Lbgam4hv/22/

Actual results:

Firefox returned an array of all 0.

Expected results:

Actual 16-bit data should have been returned.

Comment 1

[ashley_c_mort]

Here is a better exampe of what I want to do in a jsfiddle:

https://jsfiddle.net/cpm5fgzr/

let pix = new Uint16Array(size);
gl.readPixels(0, 0, w, h, gl.RGBA_INTEGER, gl.UNSIGNED_SHORT, pix);
WebGL warning: readPixels: Incompatible format or type.

Comment 2

[Kelsey Gilbert [:jgilbert]]

Attachment: Bug 1663214 - Explain what format/types ReadPixels expects.

Comment 3

[Kelsey Gilbert [:jgilbert]]

I'm really surprised, but chrome is allowing RGBA/UNSIGNED_SHORT reads from the RGBA8 backbuffer.

So I tested it, and chrome gives back IMPLEMENTATION_COLOR_READ_FORMAT/TYPE of RGBA/UNSIGNED_BYTE, but accepts RGBA/UNSIGNED_SHORT anyway, which is out of spec.

Comment 4

[Kelsey Gilbert [:jgilbert]]

I am proposing a test for this for the WebGL test suite: https://github.com/KhronosGroup/WebGL/pull/3158

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/7b5ad7a8c03d
Explain what format/types ReadPixels expects. r=lsalzman

Comment 6

[Razvan Maries]

https://hg.mozilla.org/mozilla-central/rev/7b5ad7a8c03d