167 lines
6.2 KiB
Plaintext
167 lines
6.2 KiB
Plaintext
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Name
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HP_convolution_border_modes
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Name Strings
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GL_HP_convolution_border_modes
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Version
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$Date: 1995/09/09 10:13:00 $ $Revision: 1.2 $
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Number
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67
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Dependencies
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EXT_convolution is required
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Overview
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This extension provides some additional border modes for the
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EXT_convolution extension.
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New Procedures and Functions
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None
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New Tokens
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Accepted by the <param> parameter of ConvolutionParameteriEXT,
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and ConvolutionParameterfEXT, and by the <params> parameter of
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ConvolutionParameterivEXT and ConvolutionParameterfvEXT, when the
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<pname> parameter is CONVOLUTION_BORDER_MODE_EXT:
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IGNORE_BORDER_HP
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CONSTANT_BORDER_HP
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WRAP_BORDER_HP
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Accepted by the <pname> parameter of ConvolutionParameterivEXT,
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ConvolutionParameterfvEXT, GetConvolutionParameterivEXT, and
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GetConvolutionParameterfvEXT:
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CONVOLUTION_BORDER_COLOR_HP
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Additions to Chapter 2 of the 1.0 Specification (OpenGL Operation)
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None
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Additions to Chapter 3 of the 1.0 Specification (Rasterization)
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The description of the convolution border mode is replaced with
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the following:
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The convolution border mode for a specific convolution filter is
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specified using ConvolutionParameteriEXT with the <target>
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parameter set to the name of the filter, the <pname> parameter
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set to CONVOLUTION_BORDER_MODE_EXT, and <param> set to one of
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REDUCE_EXT, IGNORE_BORDER_HP, CONSTANT_BORDER_HP, or
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WRAP_BORDER_HP.
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The width and height of source images convolved with border mode
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REDUCE_EXT are reduced by Wf-1 and Hf-1, respectively. If this
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reduction would generate a resulting image with zero or negative
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width and/or height, the output is simply null, with no error
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generated. The coordinates of the image that results from a
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convolution with border mode REDUCE_EXT are zero through Ws-Wf
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in width, and zero through Hs-Hf in height. In cases where
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errors can result from the specification of invalid image
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dimensions, it is these resulting dimensions that are tested,
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not the dimensions of the source image. (A specific example is
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TexImage1D and TexImage2D, which specify constraints for image
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dimensions. Even if TexImage1D or TexImage2D is called with a
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null pixel pointer, the dimensions of the resulting texture image
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are those that would result from the convolution of the specified
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image.)
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For the remaining border modes, we define Cw = floor(Wf / 2)
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and Ch = floor(Hf / 2). The coordinates (Cw, Ch) define the
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center of the convolution filter.
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If the convolution border mode is IGNORE_BORDER_HP, the output
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image has the same dimensions as the source image. The convolution
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filter is moved around the source image so that its center passes
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over every pixel in the source image. At each location, the sum of
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products is computed and the result is written in the destination
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image at the location that corresponds to the pixel location where
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the convolution filter is centered. However, the sum of products
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is not computed for any pixel where the convolution filter extends
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beyond one of the edges of the source image. Instead, for these
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locations, the pixel value from the source image is copied to
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the destination image.
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The convolution border mode CONSTANT_BORDER_HP is identical to
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IGNORE_BORDER_HP except that for each pixel where the convolution
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filter extends beyond one of the edges of the source image, a value
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equal to the current border color will be used as the value for
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the source image. The current convolution border color is set by
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calling ConvolutionParameterivEXT or ConvolutionParameterfvEXT with
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<pname> set to CONVOLUTION_BORDER_COLOR_HP and <params> containing
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four values that comprise the RGBA color to be used as the image
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border. Integer color components are interpreted linearly such that
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the most positive integer maps to 1.0, and the most negative integer
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maps to -1.0. Floating point color components are clamped to the
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range [0,1] when they are specified.
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If the convolution border mode is WRAP_BORDER_HP, the output image
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has the same dimensions as the source image, and the source image is
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assumed to be continuously wrapped in both x and y directions.
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Therefore, source image pixels in the Cw columns on the right edge
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are used in the convolution computation for the Cw columns on the
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right edge of the image, and vice versa. Similarly, source image
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pixels in the Ch rows on the top of the image are used in the
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convolution computation for the Ch rows on the bottom of the
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image and vice versa.
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Additions to Chapter 4 of the 1.0 Specification (Per-Fragment Operations
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and the Frame buffer)
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None
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Additions to Chapter 5 of the 1.0 Specification (Special Functions)
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None
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Additions to Chapter 6 of the 1.0 Specification (State and State Requests)
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None
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Dependencies on EXT_convolution
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EXT_convolution is required. This extension adds capability to
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the convolution operations defined in that extension.
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Errors
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INVALID_ENUM is generated if ConvolutionParameterivEXT or
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ConvolutionParameterfvEXT parameter <pname> is not
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CONVOLUTION_FILTER_SCALE_EXT, CONVOLUTION_FILTER_BIAS_EXT,
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CONVOLUTION_BORDER_MODE_EXT, or CONVOLUTION_BORDER_COLOR_HP.
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INVALID_ENUM is generated if ConvolutionParameteriEXT,
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ConvolutionParameterfEXT, ConvolutionParameterivEXT, or
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ConvolutionParameterfvEXT parameter <pname> is
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CONVOLUTION_BORDER_MODE_EXT and parameter <params> is
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not one of REDUCE_EXT, IGNORE_BORDER_HP, CONSTANT_BORDER_HP,
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or WRAP_BORDER_HP.
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INVALID_ENUM is generated if GetConvolutionParameterivEXT or
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GetConvolutionParameterfvEXT parameter <pname> is not
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CONVOLUTION_FILTER_SCALE_EXT, CONVOLUTION_FILTER_BIAS_EXT,
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CONVOLUTION_BORDER_MODE_EXT, CONVOLUTION_FORMAT_EXT,
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CONVOLUTION_WIDTH_EXT, CONVOLUTION_HEIGHT_EXT,
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MAX_CONVOLUTION_WIDTH_EXT, MAX_CONVOLUTION_HEIGHT_EXT,
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or CONVOLUTION_BORDER_COLOR_HP.
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New State
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Initial
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Get Value Get Command Type Value Attrib
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--------- ----------- ---- ------- ------
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CONVOLUTION_BORDER_COLOR_HP GetConvolutionParameterfvHP C (0,0,0,0) pixel
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New Implementation Dependent State
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None
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