GLTEXIMAGE2D(3G)

📦 version 24.3.3, in opensuse-leap 16.0

💅 GLTEXIMAGE2D(3G) 💅

okay so this is the 3G manual page, bestie — the one and only glTexImage2D is about to get the main character treatment. ✨

🌸 NAME 🌸

glTexImage2D — specify a two-dimensional texture image. Short name section, iconic behavior. 💖

🧚 C SPECIFICATION 🧚

void glTexImage2D( GLenum target,
                   GLint level,
                   GLint internalFormat,
                   GLsizei width,
                   GLsizei height,
                   GLint border,
                   GLenum format,
                   GLenum type,
                   const GLvoid *pixels )

🎀 PARAMETERS 🎀

  • target — specifies the target texture. Must be GL_TEXTURE_2D or GL_PROXY_TEXTURE_2D.
  • level — specifies the level-of-detail number. Level 0 is the base image level. Level n is the nth mipmap reduction image.
  • internalFormat — specifies the number of color components in the texture. Must be 1, 2, 3, or 4, or one of these symbolic constants: 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 — specifies the width of the texture image. Must be 2n+2(border) for some integer n. All implementations support texture images that are at least 64 texels wide.
  • height — specifies the height of the texture image. Must be 2m+2(border) for some integer m. All implementations support texture images that are at least 64 texels high.
  • border — specifies the width of the border. Must be either 0 or 1.
  • format — specifies the of the pixel data — yes, the original has a literal blank there, and I’m not gonna invent a word for it, bestie 💀. The following symbolic values are accepted: GL_COLOR_INDEX, GL_RED, GL_GREEN, GL_BLUE, GL_ALPHA, GL_RGB, GL_BGR GL_RGBA, GL_BGRA, GL_LUMINANCE, and GL_LUMINANCE_ALPHA.
  • type — specifies the data type of the pixel data. The following symbolic values are accepted: 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.
  • pixels — specifies a pointer to the image data in memory.

🦋 DESCRIPTION 🦋

Texturing maps a portion of a specified texture image onto each graphical primitive for which texturing is enabled. To enable and disable two-dimensional texturing, call glEnable and glDisable with argument GL_TEXTURE_2D. 🫶

To define texture images, call glTexImage2D. The arguments describe the parameters of the texture image, such as height, width, width of the border, level-of-detail number (see glTexParameter), and number of color components provided. The last three arguments describe how the image is represented in memory; they are identical to the pixel formats used for glDrawPixels. ✨

If target is GL_PROXY_TEXTURE_2D, no data is read from pixels, but all of the texture image state is recalculated, checked for consistency, and checked against the implementation's capabilities. If the implementation cannot handle a texture of the requested texture size, it sets all of the image state to 0, but does not generate an error (see glGetError). To query for an entire mipmap array, use an image array level greater than or equal to 1. 👑

If target is GL_TEXTURE_2D, data is read from pixels as a sequence of signed or unsigned bytes, shorts, or longs, or single-precision floating-point values, depending on type. These values are grouped into sets of one, two, three, or four values, depending on format, to form elements. If type is GL_BITMAP, the data is considered as a string of unsigned bytes (and format must be GL_COLOR_INDEX). Each data byte is treated as eight 1-bit elements, with bit ordering determined by GL_UNPACK_LSB_FIRST (see glPixelStore). 🦋

The first element corresponds to the lower left corner of the texture image. Subsequent elements progress left-to-right through the remaining texels in the lowest row of the texture image, and then in successively higher rows of the texture image. The final element corresponds to the upper right corner of the texture image. 💖

format determines the composition of each element in pixels. It can assume one of eleven symbolic values:

  • GL_COLOR_INDEX — each element is a single value, a color index. The GL converts it to fixed point (with an unspecified number of zero bits to the right of the binary point), shifted left or right depending on the value and sign of GL_INDEX_SHIFT, and added to GL_INDEX_OFFSET (see glPixelTransfer). The resulting index is converted to a set of color components using the GL_PIXEL_MAP_I_TO_R, GL_PIXEL_MAP_I_TO_G, GL_PIXEL_MAP_I_TO_B, and GL_PIXEL_MAP_I_TO_A tables, and clamped to the range [0,1].
  • GL_RED — each element is a single red component. The GL converts it to floating point and assembles it into an RGBA element by attaching 0 for green and blue, and 1 for alpha. Each component is then multiplied by the signed scale factor GL_c_SCALE, added to the signed bias GL_c_BIAS, and clamped to the range [0,1] (see glPixelTransfer).
  • GL_GREEN — each element is a single green component. The GL converts it to floating point and assembles it into an RGBA element by attaching 0 for red and blue, and 1 for alpha. Each component is then multiplied by the signed scale factor GL_c_SCALE, added to the signed bias GL_c_BIAS, and clamped to the range [0,1] (see glPixelTransfer).
  • GL_BLUE — each element is a single blue component. The GL converts it to floating point and assembles it into an RGBA element by attaching 0 for red and green, and 1 for alpha. Each component is then multiplied by the signed scale factor GL_c_SCALE, added to the signed bias GL_c_BIAS, and clamped to the range [0,1] (see glPixelTransfer).
  • GL_ALPHA — each element is a single alpha component. The GL converts it to floating point and assembles it into an RGBA element by attaching 0 for red, green, and blue. Each component is then multiplied by the signed scale factor GL_c_SCALE, added to the signed bias GL_c_BIAS, and clamped to the range [0,1] (see glPixelTransfer).
  • GL_RGB and GL_BGR — each element is an RGB triple. The GL converts it to floating point and assembles it into an RGBA element by attaching 1 for alpha. Each component is then multiplied by the signed scale factor GL_c_SCALE, added to the signed bias GL_c_BIAS, and clamped to the range [0,1] (see glPixelTransfer).
  • GL_RGBA and GL_BGRA — each element contains all four components. Each component is multiplied by the signed scale factor GL_c_SCALE, added to the signed bias GL_c_BIAS, and clamped to the range [0,1] (see glPixelTransfer).
  • GL_LUMINANCE — each element is a single luminance value. The GL converts it to floating point, then assembles it into an RGBA element by replicating the luminance value three times for red, green, and blue and attaching 1 for alpha. Each component is then multiplied by the signed scale factor GL_c_SCALE, added to the signed bias GL_c_BIAS, and clamped to the range [0,1] (see glPixelTransfer).
  • GL_LUMINANCE_ALPHA — each element is a luminance/alpha pair. The GL converts it to floating point, then assembles it into an RGBA element by replicating the luminance value three times for red, green, and blue. Each component is then multiplied by the signed scale factor GL_c_SCALE, added to the signed bias GL_c_BIAS, and clamped to the range [0,1] (see glPixelTransfer).

Refer to the glDrawPixels reference page for a description of the acceptable values for the type parameter. 📖

If an application wants to store the texture at a certain resolution or in a certain [literal blank in the original], it can request the resolution and [another literal blank in the original] with internalFormat. The GL will choose an internal representation that closely approximates that requested by internalFormat, but it may not match exactly. (The representations specified by GL_LUMINANCE, GL_LUMINANCE_ALPHA, GL_RGB, and GL_RGBA must match exactly. The numeric values 1, 2, 3, and 4 may also be used to specify the above representations.) 🌈

Use the GL_PROXY_TEXTURE_2D target to try out a resolution and update and recompute its best match for the requested storage resolution and [literal blank in the original]. To then query this state, call glGetTexLevelParameter. If the texture cannot be accommodated, texture state is set to 0. 🔥

A one-component texture image uses only the red component of the RGBA color extracted from pixels. A two-component image uses the R and A values. A three-component image uses the R, G, and B values. A four-component image uses all of the RGBA components. 💜

💅 NOTES 💅

Okay so, real talk: texturing has no effect in color index mode. Periodt.

If the GL_ARB_imaging extension is supported, RGBA elements may also be processed by the imaging pipeline. The following stages may be applied to an RGBA color before color component clamping to the range [0, 1]:

  1. Color component replacement by the color table specified for GL_COLOR_TABLE, if enabled. See glColorTable.
  2. Two-dimensional Convolution filtering, if enabled. See glConvolutionFilter1D.

If a convolution filter changes the __width of the texture (by processing with a GL_CONVOLUTION_BORDER_MODE of GL_REDUCE, for example), the width must 2n+2(height), for some integer n, and height must 2m+(border), for some integer m, after filtering.

  1. RGBA components may be multiplied by GL_POST_CONVOLUTION_c_SCALE, and added to GL_POST_CONVOLUTION_c_BIAS, if enabled. See glPixelTransfer.
  2. Color component replacement by the color table specified for GL_POST_CONVOLUTION_COLOR_TABLE, if enabled. See glColorTable.
  3. Transformation by the color matrix. See glMatrixMode.
  4. RGBA components may be multiplied by GL_POST_COLOR_MATRIX_c_SCALE, and added to GL_POST_COLOR_MATRIX_c_BIAS, if enabled. See glPixelTransfer.
  5. Color component replacement by the color table specified for GL_POST_COLOR_MATRIX_COLOR_TABLE, if enabled. See glColorTable.

The texture image can be represented by the same data formats as the pixels in a glDrawPixels command, except that GL_STENCIL_INDEX and GL_DEPTH_COMPONENT cannot be used. glPixelStore and glPixelTransfer modes affect texture images in exactly the way they affect glDrawPixels. No cap.

glTexImage2D and GL_PROXY_TEXTURE_2D are available only if the GL version is 1.1 or greater.

Internal formats other than 1, 2, 3, or 4 may be used only if the GL version is 1.1 or greater.

In GL version 1.1 or greater, pixels may be a null pointer. In this case texture memory is allocated to accommodate a texture of width width and height height. You can then download subtextures to initialize this texture memory. The image is undefined if the user tries to apply an uninitialized portion of the texture image to a primitive.

🫶 Tiny warning bestie: that “undefined” is not a vibe. Don’t rely on uninitialized texture bits.

Formats GL_BGR, and GL_BGRA and types 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 available only if the GL version is 1.2 or greater.

When the GL_ARB_multitexture extension is supported, glTexImage2D specifies the two-dimensional texture for the current texture unit, specified with glActiveTextureARB.

🚨 ERRORS 🚨

Not me listing every way this can go off the rails 😭 but here we are:

  • GL_INVALID_ENUM is generated if target is not GL_TEXTURE_2D or GL_PROXY_TEXTURE_2D.
  • GL_INVALID_ENUM is generated if format is not an accepted constant. Format constants other than GL_STENCIL_INDEX and GL_DEPTH_COMPONENT are accepted.
  • GL_INVALID_ENUM is generated if type is not a type constant.
  • GL_INVALID_ENUM is generated if type is GL_BITMAP and format is not GL_COLOR_INDEX.
  • GL_INVALID_VALUE is generated if level is less than 0.
  • GL_INVALID_VALUE may be generated if level is greater than log2max, where max is the returned value of GL_MAX_TEXTURE_SIZE.
  • GL_INVALID_VALUE is generated if internalFormat is not 1, 2, 3, 4, or one of the accepted resolution and symbolic constants.
  • GL_INVALID_VALUE is generated if width or height is less than 0 or greater than 2 + GL_MAX_TEXTURE_SIZE, or if either cannot be represented as 2k+2(border) for some integer value of k.
  • GL_INVALID_VALUE is generated if border is not 0 or 1.
  • GL_INVALID_OPERATION is generated if glTexImage2D is executed between the execution of glBegin and the corresponding execution of glEnd.
  • GL_INVALID_OPERATION is generated if type 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 type 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 format is neither GL_RGBA nor GL_BGRA.

🔎 ASSOCIATED GETS 🔎

  • glGetTexImage
  • glIsEnabled with argument GL_TEXTURE_2D

👀 SEE ALSO 👀

  • glColorTable(3G)
  • glConvolutionFilter2D(3G)
  • glCopyPixels(3G)
  • glCopyTexImage1D(3G)
  • glCopyTexImage2D(3G)
  • glCopyTexSubImage1D(3G)
  • glCopyTexSubImage2D(3G)
  • glCopyTexSubImage3D(3G)
  • glDrawPixels(3G)
  • glMatrixMode(3G)
  • glPixelStore(3G)
  • glPixelTransfer(3G)
  • glSeparableFilter2D(3G)
  • glTexEnv(3G)
  • glTexGen(3G)
  • glTexImage1D(3G)
  • glTexImage3D(3G)
  • glTexSubImage1D(3G)
  • glTexSubImage2D(3G)
  • glTexSubImage3D(3G)
  • glTexParameter(3G)

And that’s a wrap on GLTEXIMAGE2D(3G), bestie 🎀✨ The footer here is just GLTEXIMAGE2D(3G) — no extra source/version/date line in this copy to copy. 💖

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