GLGETCONVOLUTIONFILTEREXT(3GL)GLGETCONVOLUTIONFILTEREXT(3GL)NAME
glGetConvolutionFilterEXT, glGetSeparableFilterEXT - retrieve contents
of convolution image
C SPECIFICATION
void glGetConvolutionFilterEXT ( GLenum target,
GLenum format,
GLenum type,
GLvoid* image)
void glGetSeparableFilterEXT ( GLenum target,
GLenum format,
GLenum type,
GLvoid* row,
GLvoid* column,
GLvoid* span)
PARAMETERS
target The target Convolution filter. Must be GL_CONVOLUTION_1D_EXT,
or GL_CONVOLUTION_2D_EXT for glGetConvolutionFilterEXT and
GL_SEPARABLE_2D_EXT for glGetSeparableFilterEXT.
format Format of pixel data in image, row, column. Symbolic constants
GL_RGBA, GL_RED, GL_GREEN, GL_BLUE, GL_ALPHA, GL_RGB, GL_LUMI‐
NANCE, GL_LUMINANCE_ALPHA and GL_ABGR_EXT are accepted.
type Specifies the data type for pixels in image, row, column. Sym‐
bolic constants GL_UNSIGNED_BYTE, GL_BYTE, GL_UNSIGNED_SHORT,
GL_SHORT, GL_UNSIGNED_INT, GL_INT and GL_FLOAT are accepted.
image Pointer to one-dimensional array of pixel data containing con‐
tents of the convolution filter.
row Pointer to one-dimensional array of pixel data containing con‐
tents of the row convolution filter.
column Pointer to one-dimensional array of pixel data containing con‐
tents of the column convolution filter.
span Pointer to one-dimensional array of pixel data.
DESCRIPTION
glGetConvolutionFilterEXT and glGetSeparableFilterEXT are part of the
GL_EXT_convolution extension, which adds convolution to the pixel
transfer path.
glGetConvolutionFilterEXT returns in image the contents of the convolu‐
tion filter specified by target which could be GL_CONVOLUTION_1D_EXT or
GL_CONVOLUTION_2D_EXT. No pixel transfer operations are performed, but
pixel storage modes that are applicable to glReadPixels are performed.
Similarly glGetSeparableFilterEXT returns in row and column the con‐
tents of the separable convolution filter specified by target GL_SEPA‐
RABLE_2D_EXT. No change is made to any location related to <span>.
Color components are converted from the internal floating point repre‐
sentation to <type> according to table below. Prior to the conversion,
if <type> is one of GL_UNSIGNED_BYTE, GL_UNSIGNED_SHORT, or
GL_UNSIGNED_INT, the color components are clamped to 0..1, if <type> is
one of GL_BYTE, GL_SHORT, or GL_INT, the components are clamped to
-1..1. No clamping is performed if <type> is GL_FLOAT. Color components
that are requested in the specified <format>, but which are not
included in the internal format of the filter image, are returned as
zero.
Internal Component Resulting Component
__________________________________________
red red
green green
blue blue
alpha alpha
luminance red
intensity red
__________________________________________
ERRORS
GL_INVALID_ENUM is generated if target is not one of the acceptable
values.
GL_INVALID_ENUM is generated if format is not one of the acceptable
values.
GL_INVALID_ENUM is generated if type is not one of the acceptable val‐
ues.
SEE ALSO
glGetConvolutionParameterivEXT, glGetConvolutionParameterfvEXT, glCon‐
volutionFilter1DEXT, glConvolutionFilter2DEXT, glSeparableFilter2DEXT
glCopyConvolutionFilter1DEXT, glCopyConvolutionFilter2DEXT, glConvolu‐
tionParameteriEXT, glConvolutionParameterivEXT, glConvolutionParame‐
terfEXT, glConvolutionParameterfvEXT, glTexImage1D, glGetTexImage,
glDrawPixels, glCopyPixels, glReadPixels, glTexImage2D, glTexSubIm‐
age2DEXT, glCopyTexImage2DEXT, glCopyTexSubImage2DEXT, glGetTexImage,
glEnable, glDisable, glIsEnabled, glPixelStore.
1 Dec 97 GLGETCONVOLUTIONFILTEREXT(3GL)