WebGLRenderingContext.pixelStorei()

WebGLRenderingContext.pixelStorei() 是 WebGL API 中用于图像预处理的函数。

语法

void gl.pixelStorei(pname, param);

参数

pname

Glenum (en-US) 类型，表示处理的方式。关于该参数可选值，请见下面表格。

param

GLint (en-US) 类型，表示 pname 处理方式的参数。关于该参数可选值，请见下面表格。

返回值

None.

像素存储参数

模式名称 (pname) 描述 类型 默认值 param 的可选值 Specified in
gl.PACK_ALIGNMENT Packing of pixel data into memory GLint (en-US) 4 1, 2, 4, 8 OpenGL ES 2.0
gl.UNPACK_ALIGNMENT Unpacking of pixel data from memory. GLint (en-US) 4 1, 2, 4, 8 OpenGL ES 2.0
gl.UNPACK_FLIP_Y_WEBGL 如果为 true，则把图片上下对称翻转坐标轴 (图片本身不变)。 GLboolean (en-US) false true, false WebGL
gl.UNPACK_PREMULTIPLY_ALPHA_WEBGL Multiplies the alpha channel into the other color channels GLboolean (en-US) false true, false WebGL
gl.UNPACK_COLORSPACE_CONVERSION_WEBGL Default color space conversion or no color space conversion. GLenum (en-US) gl.BROWSER_DEFAULT_WEBGL gl.BROWSER_DEFAULT_WEBGL, gl.NONE WebGL

When using a WebGL 2 context, the following values are available additionally:

Constant Description Type Default value Allowed values (for param) Specified in
gl.PACK_ROW_LENGTH Number of pixels in a row. GLint (en-US) 0 0 to Infinity OpenGL ES 3.0
gl.PACK_SKIP_PIXELS Number of pixel locations skipped before the first pixel is written into memory. GLint (en-US) 0 0 to Infinity OpenGL ES 3.0
gl.PACK_SKIP_ROWS Number of rows of pixel locations skipped before the first pixel is written into memory GLint (en-US) 0 0 to Infinity OpenGL ES 3.0
gl.UNPACK_ROW_LENGTH Number of pixels in a row. GLint (en-US) 0 0 to Infinity OpenGL ES 3.0
gl.UNPACK_IMAGE_HEIGHT Image height used for reading pixel data from memory GLint (en-US) 0 0 to Infinity OpenGL ES 3.0
gl.UNPACK_SKIP_PIXELS Number of pixel images skipped before the first pixel is read from memory GLint (en-US) 0 0 to Infinity OpenGL ES 3.0
gl.UNPACK_SKIP_ROWS Number of rows of pixel locations skipped before the first pixel is read from memory GLint (en-US) 0 0 to Infinity OpenGL ES 3.0
gl.UNPACK_SKIP_IMAGES Number of pixel images skipped before the first pixel is read from memory GLint (en-US) 0 0 to Infinity OpenGL ES 3.0

Examples

Setting the pixel storage mode affects the WebGLRenderingContext.readPixels() operations, as well as unpacking of textures with the WebGLRenderingContext.texImage2D() and WebGLRenderingContext.texSubImage2D() (en-US) methods.

js

var tex = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D, tex);
gl.pixelStorei(gl.PACK_ALIGNMENT, 4);

To check the values for packing and unpacking of pixel data, you can query the same pixel storage parameters with WebGLRenderingContext.getParameter().

js

gl.getParameter(gl.PACK_ALIGNMENT);
gl.getParameter(gl.UNPACK_ALIGNMENT);

Specifications

Specification
WebGL Specification
# 5.14.3
WebGL Specification
# PIXEL_STORAGE_PARAMETERS
WebGL 2.0 Specification
# 3.7.2

Browser compatibility

BCD tables only load in the browser

See also