GLCONVOLUTIONFILTER2D

NAME

C SPECIFICATION

                              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 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.

image

Pointer to a two-dimensional array of pixel data that is processed to build the convolution filter kernel.

DESCRIPTION

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 completed.

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 internalformat. 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:

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 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

ERRORS

ASSOCIATED GETS

SEE ALSO