1991-2006 Silicon Graphics, Inc.
glGetSeparableFilter 3G
glGetSeparableFilter get separable convolution filter kernel images

## C Specification

void `glGetSeparableFilter` GLenum target GLenum format GLenum type GLvoid * row GLvoid * column GLvoid * span

## Parameters

target

  The separable filter to be retrieved. Must be `GL_SEPARABLE_2D`.

format

  Format of the output images. Must be one of `GL_RED`, `GL_GREEN`, `GL_BLUE`, `GL_ALPHA`, `GL_RGB`, `GL_BGR` `GL_RGBA`, `GL_BGRA`, `GL_LUMINANCE`, or `GL_LUMINANCE_ALPHA`.

type

  Data type of components in the output images. 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 storage for the row filter image.

column

  Pointer to storage for the column filter image.

span

  Pointer to storage for the span filter image (currently unused).

## Description

`glGetSeparableFilter` returns the two one-dimensional filter kernel images for the current separable 2D convolution filter. The row image is placed in row and the column image is placed in column according to the specifications in format and type. (In the current implementation, span is not affected in any way.) No pixel transfer operations are performed on the images, but the relevant pixel storage modes are applied.

If a non-zero named buffer object is bound to the `GL_PIXEL_PACK_BUFFER` target (see glBindBuffer) while a separable convolution filter is requested, row, column, and span are treated as a byte offset into the buffer object's data store.

Color components that are present in format but not included in the internal format of the filters are returned as zero. The assignments of internal color components to the components of format are as follows:

Internal Component | Resulting Component
--- | ---
Red | Red
Green | Green
Blue | Blue
Alpha | Alpha
Luminance | Red
Intensity | Red

## Notes

`glGetSeparableFilter` is present only if `ARB_imaging` is returned when glGetString is called with an argument of `GL_EXTENSIONS`.

Non-separable 2D filters must be retrieved with glGetConvolutionFilter.

## Errors

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

`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 type 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 type 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`.

`GL_INVALID_OPERATION` is generated if a non-zero buffer object name is bound to the `GL_PIXEL_PACK_BUFFER` target and the buffer object's data store is currently mapped.

`GL_INVALID_OPERATION` is generated if a non-zero buffer object name is bound to the `GL_PIXEL_PACK_BUFFER` target and the data would be packed to the buffer object such that the memory writes required would exceed the data store size.

`GL_INVALID_OPERATION` is generated if a non-zero buffer object name is bound to the `GL_PIXEL_PACK_BUFFER` target and row or column is not evenly divisible into the number of bytes needed to store in memory a datum indicated by type.

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

## Associated Gets

glGetConvolutionParameter

glGet with argument `GL_PIXEL_PACK_BUFFER_BINDING`

## See Also

glGetConvolutionFilter, glConvolutionParameter, glSeparableFilter2D

## Copyright

Copyright 1991-2006 Silicon Graphics, Inc. This document is licensed under the SGI Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/.