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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() (en-US) operations, as well as unpacking of textures with the WebGLRenderingContext.texImage2D() and WebGLRenderingContext.texSubImage2D() (en-US) methods.
 

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().

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

Specifications

Specification Status Comment
WebGL 1.0
pixelStorei		 Recommendation Initial definition for WebGL.
WebGL 1.0
Pixel Storage Parameters		 Recommendation Additional pixel storage parameters that aren't specified in OpenGL.
OpenGL ES 2.0
glPixelStorei		 Standard Man page of the OpenGL ES 2.0 API.
WebGL 2.0
pixelStorei		 Editor's Draft Updated definition for WebGL 2.
OpenGL ES 3.0
glPixelStorei		 Standard Man page of the OpenGL ES 3.0 API.

Browser compatibility

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See also