I get invalid type error when calling readPixels

WebGL Fundamentals

WebGL Using 2 or More Textures WebGL Implementing DrawImage WebGL 2D Matrices WebGL Implementing A Matrix Stack WebGL 2D Rotation WebGL 2D Scale WebGL 2D Translation WebGL - Rasterization vs 3D libraries WebGL 3D - Cameras WebGL 3D Geometry - Lathe WebGL 3D - Directional Lighting WebGL 3D - Point Lighting WebGL 3D - Normal Mapping WebGL 3D - Spot Lighting WebGL - Orthographic 3D WebGL 3D Perspective Correct Texture Mapping WebGL 3D Perspective WebGL Textures WebGL and Alpha WebGL - Animation WebGL Anti-Patterns WebGL Attributes WebGL Boilerplate WebGL - Cross Origin Images WebGL Cross Platform Issues WebGL Cubemaps WebGL 3D - Data Textures WebGL - Drawing Multiple Things WebGL Drawing Without Data WebGL Environment Maps (reflections) WebGL Fog WebGL Framebuffers WebGL Fundamentals WebGL GPGPU WebGL How It Works WebGL Image Processing Continued WebGL Image Processing WebGL Indexed Vertices WebGL Optimization - Instanced Drawing WebGL - Less Code, More Fun WebGL Load Obj with Mtl WebGL Load Obj WebGL Matrices vs Math Matrices WebGL Multiple Views, Multiple Canvases WebGL Picking WebGL Planar and Perspective Projection Mapping WebGL Points, Lines, and Triangles WebGL Post Processing WebGL Precision Issues WebGL Pulling Vertices Accessing textures by pixel coordinate in WebGL2 A simple way to show the load on the GPU's vertex and fragment processing? Apply a displacement map and specular map Can anyone explain what this GLSL fragment shader is doing? Can I mute the warning about vertex attrib 0 being disabled? Create image warping effect in WebGL Creating a smudge/liquify effect How to draw Depth Sprites Determine min/max values for the entire image Don't blend a polygon that crosses itself Drawing 2D image with depth map to achieve pseudo-3D effect Drawing a heightmap Drawing layers with different points Drawing Many different models in a single draw call Drawing textured sprites with instanced drawing Efficient particle system in javascript? (WebGL) Emulating palette based graphics in WebGL FPS-like camera movement with basic matrix transformations Get the size of a point for collision checking GLSL shader to support coloring and texturing How can I compute for 500 points which of 1000 line segments is nearest to each point? How can I create a 16bit historgram of 16bit data How can I get all the uniforms and uniformBlocks How can I move the perspective vanishing point from the center of the canvas? How to Achieve Moving Line with Trail Effects How to bind an array of textures to a WebGL shader uniform? How to blend colors across 2 triangles How to combine more text drawing into fewer draw calls How to control the color between vertices How to create a torus How to detect clipped triangles in the framgment shader How to determine the average brightness in a scene? How to draw correctly textured trapezoid polygons How to fade the drawing buffer How to figure out how much GPU work to do without crashing WebGL How to get audio data into a shader How to get code completion for WebGL in Visual Studio Code How to get the 3d coordinates of a mouse click How to get pixelize effect in webgl? How to implement zoom from mouse in 2D WebGL How to import a heightmap in WebGL How to load images in the background with no jank How to make a smudge brush tool How to make WebGL canvas transparent How to optimize rendering a UI How to prevent texture bleeding with a texture atlas How to process particle positions How to read a single component with readPixels How to render large scale images like 32000x32000 How to simulate a 3D texture in WebGL

WebGLFundame · 2025-02-26 · via WebGL Fundamentals

Question:

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.

Answer:

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

此内容由惯性聚合(RSS阅读器)自动聚合整理，仅供阅读参考。原文来自 — 版权归原作者所有。

推荐订阅源

WebGL Fundamentals

Question:

Answer: