gl-texture2d

gl-texture2d

WebGL texture object wrapper

Example

Try it in your browser right now

var shell         = require("gl-now")()
var createShader  = require("gl-shader")
var createTexture = require("gl-texture2d")
var drawTriangle  = require("a-big-triangle")
var baboon        = require("baboon-image")
var glslify       = require("glslify")

var createShader = glslify({
  vertex:"\
    attribute vec2 position;\
    varying vec2 texCoord;\
    void main() {\
      gl_Position = vec4(position, 0, 1);\
      texCoord = vec2(0.0,1.0)+vec2(0.5,-0.5) * (position + 1.0);\
    }", 
  fragment: "\
    precision highp float;\
    uniform sampler2D texture;\
    varying vec2 texCoord;\
    void main() {\
      gl_FragColor = texture2D(texture, texCoord);\
    }",
  inline: true
})

var shader, texture

shell.on("gl-init", function() {
  var gl = shell.gl
  
  //Create texture
  texture = createTexture(gl, baboon)

  //Create shader
  shader = createShader(gl)
  shader.attributes.position.location = 0
})

shell.on("gl-render", function() {
  //Draw it
  shader.bind()
  shader.uniforms.texture = texture.bind()
  drawTriangle(shell.gl)
})

Here is what it should look like:

Install

npm install gl-texture2d

API

var createTexture = require("gl-texture2d")

Constructor

There are three basic usage patterns for createTexture:

var tex = createTexture(gl, shape[, format, type])

Creates an unitialized texture with the given dimensions and format

• shape is a length 2 array representing the [width, height] of the texture
• format (optional) is the format of the texture (default gl.RGBA)
• type is the type of texture (default gl.UNSIGNED_BYTE)

var tex = createTexture(gl, domElement[, format, type])

Creates a texture from the given data source. Where domElement is one of the following items:

• An ImageData object
• An HTMLCanvas object
• An HTMLImage object
• An HTMLVideo object

And format is an OpenGL data format or defaults to gl.RGBA and type is the storage type which defaults to gl.UNSIGNED_BYTE

var tex = createTexture(gl, array)

Creates a texture from an ndarray. The rules for selecting the format and type depend on the shape of the ndarray. The type of the texture is inferred according to the following rules. Let:

• dtype = ndarray.dtype(array)
• shape = array.shape

Then the rules for type and format are defined according to the following table:

dtype	shape	format	type
float*	[w,h]	LUMINANCE	FLOAT
float*	[w,h,1]	ALPHA	FLOAT
float*	[w,h,2]	LUMINANCE_ALPHA	FLOAT
float*	[w,h,3]	RGB	FLOAT
float*	[w,h,4]	RGBA	FLOAT
(u)int*	[w,h]	LUMINANCE	UNSIGNED_BYTE
(u)int*	[w,h,1]	ALPHA	UNSIGNED_BYTE
(u)int*	[w,h,2]	LUMINANCE_ALPHA	UNSIGNED_BYTE
(u)int*	[w,h,3]	RGB	UNSIGNED_BYTE
(u)int*	[w,h,4]	RGBA	UNSIGNED_BYTE

Other combinations of shape and dtype are invalid and throw an error.

Texture Methods

tex.bind([texUnit])

Binds the texture for use. Basically a short cut for:

gl.activeTexture(gl.TEXTURE0 + texUnit)
gl.bindTexture(gl.TEXTURE_2D, this.handle)

If texUnit is not specified then the active texture is not changed.

Returns The texture unit the texture is bound to.

`tex.dispose()``

Destroys the texture object and releases all of its resources. Under the hood this is equivalent to:

gl.deleteTexture(this.handle)

tex.setPixels(data[, offset, mipLevel])

Unpacks data into a subregion of the texture. As before in the constructor data can be either an ndarray, HTMLCanvas, HTMLImage or HTMLVideo object. If data is an ndarray it must have a compatible format with the initial array layout.

• offset is a length 2 array representing the offset into which the pixels will be written in [x,y]. (Default: [0,0])
• mipLevel is the mip level to write to. (Default 0)

If data is an ndarray the same rules as in the constructor are followed for converting the type of the buffer.

tex.generateMipmap()

Generates mipmaps for the texture. This will fail if the texture dimensions are not a power of two.

Texture Properties

tex.shape

An array representing the dimensions of the texture in [width, height]. Writing to this value will resize the texture and invalidate its contents. For example, to resize the texture tex to the shape [newWidth, newHeight] you can do:

tex.shape = [newWidth, newHeight]

tex.wrap

Texture wrap around behavior for x/y of the texture. Used to set/get [gl.TEXTURE_WRAP_T, gl.TEXTURE_WRAP_S]. Defaults to [gl.CLAMP_TO_EDGE, gl.CLAMP_TO_EDGE]. To update this value, write to it with a vector. For example,

tex.wrap = [gl.MIRRORED_REPEAT, gl.REPEAT]

Or you can update it with a single value to set the wrap mode for both axes:

tex.wrap = gl.REPEAT

tex.magFilter

Magnification filter. Used to set/get gl.TEXTURE_MAG_FILTER. Defaults to gl.NEAREST

tex.minFilter

Minification filter. Used to set/get gl.TEXTURE_MIN_FILTER. Defaults to gl.NEAREST

tex.mipSamples

The number of anisotropic filtering samples to use. This requires EXT_texture_filter_anisotropic to have any effect. High values will improve mipmap quality, but decrease performance.

Internals

tex.gl

A reference to the WebGL context of the texture.

tex.handle

A handle to the underlying texture object.

tex.format

The internal format of the texture.

tex.type

The internal data type of the texture.

Credits

(c) 2013-2014 Mikola Lysenko. MIT License