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
No compatibility data found for api/WebGLRenderingContext.
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