glSeparableFilter2D
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## Name

glSeparableFilter2D — define a separable two-dimensional convolution filter

## C Specification

`void `glSeparableFilter2D`` | `(` | `GLenum `target`, GLenum `internalformat`, GLsizei `width`, GLsizei `height`, GLenum `format`, GLenum `type`, const GLvoid *`row`, const GLvoid *`column`);`

## Python Specification

``glSeparableFilter2D`` | `(` | ``target`, `internalformat`, `width`, `height`, `format`, `type`, `row`, `column`) → `None``

## Parameters

`target`
  Must be `GL_SEPARABLE_2D`.
`internalformat`
  The internal of the convolution filter kernel. The allowable values are `GL_ALPHA`, `GL_ALPHA4`, `GL_ALPHA8`, `GL_ALPHA12`, `GL_ALPHA16`, `GL_LUMINANCE`, `GL_LUMINANCE4`, `GL_LUMINANCE8`, `GL_LUMINANCE12`, `GL_LUMINANCE16`, `GL_LUMINANCE_ALPHA`, `GL_LUMINANCE4_ALPHA4`, `GL_LUMINANCE6_ALPHA2`, `GL_LUMINANCE8_ALPHA8`, `GL_LUMINANCE12_ALPHA4`, `GL_LUMINANCE12_ALPHA12`, `GL_LUMINANCE16_ALPHA16`, `GL_INTENSITY`, `GL_INTENSITY4`, `GL_INTENSITY8`, `GL_INTENSITY12`, `GL_INTENSITY16`, `GL_R3_G3_B2`, `GL_RGB`, `GL_RGB4`, `GL_RGB5`, `GL_RGB8`, `GL_RGB10`, `GL_RGB12`, `GL_RGB16`, `GL_RGBA`, `GL_RGBA2`, `GL_RGBA4`, `GL_RGB5_A1`, `GL_RGBA8`, `GL_RGB10_A2`, `GL_RGBA12`, or `GL_RGBA16`.
`width`
  The number of elements in the pixel array referenced by `row`. (This is the width of the separable filter kernel.)
`height`
  The number of elements in the pixel array referenced by `column`. (This is the height of the separable filter kernel.)
`format`
  The of the pixel data in `row` and `column`. The allowable values are `GL_RED`, `GL_GREEN`, `GL_BLUE`, `GL_ALPHA`, `GL_RGB`, `GL_BGR`, `GL_RGBA`, `GL_BGRA`, `GL_INTENSITY`, `GL_LUMINANCE`, and `GL_LUMINANCE_ALPHA`.
`type`
  The type of the pixel data in `row` and `column`. Symbolic constants `GL_UNSIGNED_BYTE`, `GL_BYTE`, `GL_BITMAP`, `GL_UNSIGNED_SHORT`, `GL_SHORT`, `GL_UNSIGNED_INT`, `GL_INT`, `GL_FLOAT`, `GL_UNSIGNED_BYTE_3_3_2`, `GL_UNSIGNED_BYTE_2_3_3_REV`, `GL_UNSIGNED_SHORT_5_6_5`, `GL_UNSIGNED_SHORT_5_6_5_REV`, `GL_UNSIGNED_SHORT_4_4_4_4`, `GL_UNSIGNED_SHORT_4_4_4_4_REV`, `GL_UNSIGNED_SHORT_5_5_5_1`, `GL_UNSIGNED_SHORT_1_5_5_5_REV`, `GL_UNSIGNED_INT_8_8_8_8`, `GL_UNSIGNED_INT_8_8_8_8_REV`, `GL_UNSIGNED_INT_10_10_10_2`, and `GL_UNSIGNED_INT_2_10_10_10_REV` are accepted.
`row`
  Pointer to a one-dimensional array of pixel data that is processed to build the row filter kernel.
`column`
  Pointer to a one-dimensional array of pixel data that is processed to build the column filter kernel.

## Description

`glSeparableFilter2D` builds a two-dimensional separable convolution filter kernel from two arrays of pixels. The pixel arrays specified by (`width`, `format`, `type`, `row`) and (`height`, `format`, `type`, `column`) are processed just as if they had been passed to `glDrawPixels`, but processing stops after the final expansion to RGBA is completed. Next, the R, G, B, and A components of all pixels in both arrays are scaled by the four separable 2D `GL_CONVOLUTION_FILTER_SCALE` parameters and biased by the four separable 2D `GL_CONVOLUTION_FILTER_BIAS` parameters. (The scale and bias parameters are set by `glConvolutionParameter` using the `GL_SEPARABLE_2D` target and the names `GL_CONVOLUTION_FILTER_SCALE` and `GL_CONVOLUTION_FILTER_BIAS`. The parameters themselves are vectors of four values that are applied to red, green, blue, and alpha, in that order.) The R, G, B, and A values are not clamped to [0,1] at any time during this process. Each pixel is then converted to the internal specified by `internalformat`. This conversion simply maps the component values of the pixel (R, G, B, and A) to the values included in the internal (red, green, blue, alpha, luminance, and intensity). The mapping is as follows:

Internal Format | Red | Green | Blue | Alpha | Luminance | Intensity
`GL_LUMINANCE` |  |  |  |  | R |
`GL_LUMINANCE_ALPHA` |  |  |  | A | R |
`GL_INTENSITY` |  |  |  |  |  | R
`GL_RGB` | R | G | B |  |  |
`GL_RGBA` | R | G | B | A |  |

The red, green, blue, alpha, luminance, and/or intensity components of the resulting pixels are stored in floating-point rather than integer They form two one-dimensional filter kernel images. The row image is indexed by coordinate `i` starting at zero and increasing from left to right. Each location in the row image is derived from element `i` of `row`. The column image is indexed by coordinate `j` starting at zero and increasing from bottom to top. Each location in the column image is derived from element `j` of `column`.

Note that after a convolution is performed, the resulting color components are also scaled by their corresponding `GL_POST_CONVOLUTION_c_SCALE` parameters and biased by their corresponding `GL_POST_CONVOLUTION_c_BIAS` parameters (where `c` takes on the values RED, GREEN, BLUE, and ALPHA). These parameters are set by `glPixelTransfer`.

## Notes

`glSeparableFilter2D` is present only if `GL_ARB_imaging` is returned when `glGetString` is called with an argument of `GL_EXTENSIONS`.

## Errors

`GL_INVALID_ENUM` is generated if `target` is not `GL_SEPARABLE_2D`.

`GL_INVALID_ENUM` is generated if `internalformat` is not one of the allowable values.

`GL_INVALID_VALUE` is generated if `width` is less than zero or greater than the maximum supported value. This value may be queried with `glGetConvolutionParameter` using target `GL_SEPARABLE_2D` and name `GL_MAX_CONVOLUTION_WIDTH`.

`GL_INVALID_VALUE` is generated if `height` is less than zero or greater than the maximum supported value. This value may be queried with `glGetConvolutionParameter` using target `GL_SEPARABLE_2D` and name `GL_MAX_CONVOLUTION_HEIGHT`.

`GL_INVALID_ENUM` is generated if `format` is not one of the allowable values.

`GL_INVALID_ENUM` is generated if `type` is not one of the allowable values.

`GL_INVALID_OPERATION` is generated if `glSeparableFilter2D` is executed between the execution of `glBegin` and the corresponding execution of `glEnd`.

`GL_INVALID_OPERATION` is generated if `height` is one of `GL_UNSIGNED_BYTE_3_3_2`, `GL_UNSIGNED_BYTE_2_3_3_REV`, `GL_UNSIGNED_SHORT_5_6_5`, or `GL_UNSIGNED_SHORT_5_6_5_REV` and `format` is not `GL_RGB`.

`GL_INVALID_OPERATION` is generated if `height` is one of `GL_UNSIGNED_SHORT_4_4_4_4`, `GL_UNSIGNED_SHORT_4_4_4_4_REV`, `GL_UNSIGNED_SHORT_5_5_5_1`, `GL_UNSIGNED_SHORT_1_5_5_5_REV`, `GL_UNSIGNED_INT_8_8_8_8`, `GL_UNSIGNED_INT_8_8_8_8_REV`, `GL_UNSIGNED_INT_10_10_10_2`, or `GL_UNSIGNED_INT_2_10_10_10_REV` and `format` is neither `GL_RGBA` nor `GL_BGRA`.

## Associated Gets

`glGetConvolutionParameter`, `glGetSeparableFilter`

## See Also

glConvolutionFilter1D, glConvolutionFilter2D, glConvolutionParameter, glPixelTransfer

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