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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 (C) 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				    06/10/2014			 GLCONVOLUTIONFILTER2(3G)
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