glSeparableFilter2D — define a separable two-dimensional convolution filter
void glSeparableFilter2D( | GLenum | target, |
| GLenum | internalformat, | |
| GLsizei | width, | |
| GLsizei | height, | |
| GLenum | format, | |
| GLenum | type, | |
| const GLvoid * | row, | |
| const GLvoid * | column); |
target
Must be GL_SEPARABLE_2D.
internalformat
The internal format 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 format 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.
rowPointer to a one-dimensional array of pixel data that is processed to build the row filter kernel.
columnPointer to a one-dimensional array of pixel data that is processed to build the column filter kernel.
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.
If a non-zero named buffer object is bound to the GL_PIXEL_UNPACK_BUFFER target
(see glBindBuffer) while a convolution filter is
specified, row and column are treated as byte offsets into the buffer object's data store.
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 format 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 format (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
format.
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.
glSeparableFilter2D is present only if ARB_imaging is returned when glGetString
is called with an argument of GL_EXTENSIONS.
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_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_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_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.
GL_INVALID_OPERATION is generated if a non-zero buffer object name is bound to the
GL_PIXEL_UNPACK_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_UNPACK_BUFFER target and the data would be unpacked from the buffer
object such that the memory reads 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_UNPACK_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 glSeparableFilter2D is executed
between the execution of glBegin and the corresponding
execution of glEnd.
glGetConvolutionParameter, glGetSeparableFilter
glGet with argument GL_PIXEL_UNPACK_BUFFER_BINDING
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/.