GLCONVOLUTIONFILTER1D(3G)

📦 version 24.3.3, in opensuse-leap 16.0

✨ GLCONVOLUTIONFILTER1D ✨

okay bestie, welcome to the 3G section of the manual 💅 this one's called glConvolutionFilter1D and it's literally about building 1D convolution filter kernels. no cap. let's get into it 🦋

🌸 NAME 🌸

glConvolutionFilter1D — define a one-dimensional convolution filter 💖

🌈 C SPECIFICATION 🌈

void glConvolutionFilter1D( GLenum target,
                            GLenum internalformat,
                            GLsizei width,
                            GLenum format,
                            GLenum type,
                            const GLvoid *image )

🎀 PARAMETERS 🎀

  • target — has to be GL_CONVOLUTION_1D. that's it. that's the only vibe it accepts ✨
  • internalformat — the internal format of the convolution filter kernel. the allowable values are GL_ALPHA, GL_LUMINANCE, GL_LUMINANCE_ALPHA, GL_INTENSITY, GL_RGB, and GL_RGBA 👑
  • width — the width of the pixel array that image points at 📏
  • format — the format of the pixel data in image. 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. yeah that's a lot, she's thorough 💀
  • type — the type of the pixel data in image. the 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 one-dimensional array of pixel data that gets processed to build the convolution filter kernel 📸

💜 DESCRIPTION 💜

glConvolutionFilter1D builds a one-dimensional convolution filter kernel out of an array of pixels. periodt ✨

the pixel array you specified with width, format, type, and image gets extracted from memory and processed exactly as if glDrawPixels were called — except the processing stops right after the final expansion to RGBA is done. no further, bestie, that's the whole journey 🚶‍♀️

next, the R, G, B, and A components of each pixel get scaled by the four 1D GL_CONVOLUTION_FILTER_SCALE parameters and biased by the four 1D GL_CONVOLUTION_FILTER_BIAS parameters. (those scale and bias parameters are set by glConvolutionParameter using the GL_CONVOLUTION_1D target and the names GL_CONVOLUTION_FILTER_SCALE and GL_CONVOLUTION_FILTER_BIAS. the parameters themselves are vectors of four values, applied to red, green, blue, and alpha, in that order. iykyk 🎯) and listen — the R, G, B, and A values are not clamped to [0,1] at any point during this whole process. not once. she refuses 🔥

then each pixel gets converted to the internal format specified by internalformat. this conversion is honestly simple: it just maps the component values of the pixel (R, G, B, and A) onto the values included in the internal format (red, green, blue, alpha, luminance, and intensity). the mapping goes like this 👇

Internal Format      Red   Green   Blue   Alpha   Luminance   Intensity
────────────────────────────────────────────────────────────────────────
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 one-dimensional filter kernel image indexed with coordinate i such that i starts at 0 and increases from left to right 🦋 kernel location i is derived from the ith pixel, counting from 0 🧮

okay so heads up — 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). those parameters are set by glPixelTransfer. yes, there's a second round of scaling. she's doing the most, respectfully 💅

⭐ NOTES ⭐

glConvolutionFilter1D is present only if GL_ARB_imaging is returned when glGetString is called with an argument of GL_EXTENSIONS. so check first, bestie, or you'll be sad 😭

💀 ERRORS 💀

  • GL_INVALID_ENUM is generated if target is not GL_CONVOLUTION_1D.
  • GL_INVALID_ENUM is generated if internalformat 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. that value can be queried with glGetConvolutionParameter using target GL_CONVOLUTION_1D and name GL_MAX_CONVOLUTION_WIDTH 📐
  • 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_OPERATION is generated if glConvolutionFilter1D is executed between the execution of glBegin and the corresponding execution of glEnd. just… don't do that 🙈
  • GL_INVALID_OPERATION is generated if format 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 type is not GL_RGB.
  • GL_INVALID_OPERATION is generated if format 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 type is neither GL_RGBA nor GL_BGRA.

🔍 ASSOCIATED GETS 🔍

  • glGetConvolutionParameter
  • glGetConvolutionFilter

👑 SEE ALSO 👑

  • glConvolutionFilter2D(3G)
  • glSeparableFilter2D(3G)
  • glConvolutionParameter(3G)
  • glPixelTransfer(3G)

and that's the whole page, bestie!! 🫶 this one's from the 3G manual — GLCONVOLUTIONFILTER1D(3G), that's the source/version tag it signs off with 🌸 no date on this one, she's timeless like that. go forth and convolve, you absolute icon 💖✨🎀

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