glConvolutionFilter2D man page on Darwin

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GLCONVOLUTIONFILTER2D(3G)			     GLCONVOLUTIONFILTER2D(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 *image )

PARAMETERS
       target	       Must be GL_CONVOLUTION_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 width of the pixel array referenced by image.

       height	       The height of the pixel array referenced by image.

       format	       The   of the pixel data in image.  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  image.	Symbolic  con‐
		       stants	  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.

       image	       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  ker‐
       nel from an array of pixels.

       The  pixel array specified by width, height, format, type, and image is
       extracted from memory  and  processed  just  as	if  glDrawPixels  were
       called,	but processing stops after the final expansion to RGBA is com‐
       pleted.

       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  specified by internalfor‐
       mat.  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	    Channel mapping
	GL_ALPHA	    A=Alpha
	GL_LUMINANCE	    R=Luminance
	GL_LUMINANCE_ALPHA  A=Alpha, R=Luminance
	GL_INTENSITY	    R=Intensity
	GL_RGB		    R=Red, G=Green, B=Blue
	GL_RGBA		    R=Red, G=Green, B=Blue, A=Alpha

       The  red, green, blue, alpha, luminance, and/or intensity components of
       the resulting pixels are stored in floating-point rather	 than  integer
       They  form  a  two-dimensional filter kernel image indexed with coordi‐
       nates 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	compo‐
       nents	  are	   also	     scaled	by     their	 corresponding
       GL_POST_CONVOLUTION_c_SCALE parameters and biased by their  correspond‐
       ing  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 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_CONVOLUTION_2D.

       GL_INVALID_ENUM is generated if internalformat is not one of the allow‐
       able 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_ENUM is generated if format is not one of the allowable val‐
       ues.

       GL_INVALID_ENUM is generated if type is not one of the  allowable  val‐
       ues.

       GL_INVALID_OPERATION  is generated if glConvolutionFilter2D 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  for‐
       mat is neither GL_RGBA nor GL_BGRA.

ASSOCIATED GETS
       glGetConvolutionParameter, glGetConvolutionFilter

SEE ALSO
       glConvolutionFilter1D,	glSeparableFilter2D,   glConvolutionParameter,
       glPixelTransfer

						     GLCONVOLUTIONFILTER2D(3G)
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