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I get invalid type error when calling readPixels


context.readPixels(0, 0, context.drawingBufferWidth, context.drawingBufferHeight, context.RGBA, context.FLOAT, pixels);

This is the code. I get this error in the console: WebGL: INVALID_ENUM: readPixels: invalid type

But this works perfectly fine:

context.readPixels(0, 0, context.drawingBufferWidth, context.drawingBufferHeight, context.RGBA, context.UNSIGNED_BYTE, pixels);

Float or int is supposed to be supported, but only unsigned_byte works. There's no resource online on how to correctly apply a type that seems to work. Everything follows a different pattern.


FLOAT is not guaranteed to be supported. The only format/type combination that is guaranteed to be supported is RGBA/UNSIGNED_BYTE. See Spec, section 4.3.1

After that one other implementation dependent format/type combo might be supported depending on the type of thing you're reading. You can query that with

const altFormat = gl.getParameter(gl.IMPLEMENTATION_COLOR_READ_FORMAT);
const altType = gl.getParameter(gl.IMPLEMENTATION_COLOR_READ_TYPE);

The code above makes a RGBA/FLOAT texture and attached it to a framebuffer then checks the alternate format/type combo to read it. On Chrome it gets RGBA/UNSIGNED_BYTE, on Firefox it gets RGBA/FLOAT. Both are valid responses since the alternate combo is implementation dependent.

The question and quoted portions thereof are CC BY-SA 4.0 by Tony Arntsen from here
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