glConvolutionFilter2D man page on RedHat
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GLCONVOLUTIONFILTER2(3G) OpenGL Manual GLCONVOLUTIONFILTER2(3G)
NAME
glConvolutionFilter2D - define a two-dimensional convolution filter
C SPECIFICATION
void glConvolutionFilter2D(GLenum target, GLenum internalformat,
GLsizei width, GLsizei height,
GLenum format, GLenum type,
const GLvoid * data);
PARAMETERS
target
Must be GL_CONVOLUTION_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 width of the pixel array referenced by data.
height
The height of the pixel array referenced by data.
format
The format of the pixel data in data. The allowable values are
GL_RED, GL_GREEN, GL_BLUE, GL_ALPHA, GL_RGB, GL_BGR, GL_RGBA,
GL_BGRA, GL_LUMINANCE, and GL_LUMINANCE_ALPHA.
type
The type of the pixel data in data. 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.
data
Pointer to a two-dimensional array of pixel data that is processed
to build the convolution filter kernel.
DESCRIPTION
glConvolutionFilter2D builds a two-dimensional convolution filter
kernel from an array of pixels.
The pixel array specified by width, height, format, type, and data is
extracted from memory and processed just as if glDrawPixels() were
called, 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, data is treated as a byte offset into the buffer
object's data store.
The R, G, B, and A components of each pixel are next scaled by the four
2D GL_CONVOLUTION_FILTER_SCALE parameters and biased by the four 2D
GL_CONVOLUTION_FILTER_BIAS parameters. (The scale and bias parameters
are set by glConvolutionParameter() using the GL_CONVOLUTION_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 │ Red │ Green │ Blue │ Alpha │ Luminance │ Intensity │
│Format │ │ │ │ │ │ │
│ │ │ │ │ │ │ │
├─────────────────────────────────┼─────────────────────────────┼───────────────────────────────┼──────────────────────────────┼───────────────────────────────┼───────────────────────────────────┼───────────────────────────────────┤
│GL_ALPHA │ │ │ │ A │ │ │
├─────────────────────────────────┼─────────────────────────────┼───────────────────────────────┼──────────────────────────────┼───────────────────────────────┼───────────────────────────────────┼───────────────────────────────────┤
│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 a two-dimensional filter kernel image indexed with
coordinates i and j such that i starts at zero and increases from left
to right, and j starts at zero and increases from bottom to top. Kernel
location i,j is derived from the Nth pixel, where N is i+j*width.
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
glConvolutionFilter2D is present only if 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_CONVOLUTION_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_CONVOLUTION_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_CONVOLUTION_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 data 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 glConvolutionFilter2D is executed
between the execution of glBegin() and the corresponding execution of
glEnd().
ASSOCIATED GETS
glGetConvolutionParameter(), glGetConvolutionFilter()
SEE ALSO
glConvolutionFilter1D(), glSeparableFilter2D(),
glConvolutionParameter(), glPixelTransfer()
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/.
AUTHORS
opengl.org
opengl.org 03/16/2013 GLCONVOLUTIONFILTER2(3G)
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