glColorSubTableEXT

  • Article

The glColorSubTableEXT function specifies a portion of the targeted texture's palette to be replaced.

void glColorSubTableEXT(
  GLenum target,  GLsizei start,  GLsizei count,  GLenum format,  GLenum type,  const GLvoid *data);

Parameters

  • target
    The target paletted texture that is to have its palette changed. Must be TEXTURE_1D or TEXTURE_2D.

  • start
    The starting palette index entry of the palette to be changed.

  • count
    The number of palette index entries of the palette to be changed beginning at start. The count parameter determines the range of palette index entries that are changed.

  • format
    The format of the pixel data. The following symbolic constants are accepted:

    Constant Description
    GL_RGBA Each pixel is a group of four components in the following order: red, green, blue, alpha. The RGBA format is determined in this way:
    1. The glColorSubTableEXT function converts floating-point values directly to an internal format with unspecified precision. Signed integer values are mapped linearly to the internal format such that the most positive representable integer value maps to 1.0, and the most negative representable value maps to 1.0. Unsigned integer data is mapped similarly: the largest integer value maps to 1.0, and zero maps to 0.0.
    2. The glColorSubTableEXT function multiplies the resulting color values by GL_c_SCALE and adds them to GL_c_BIAS, where c is RED, GREEN, BLUE, and ALPHA for the respective color components. The results are clamped to the range [0,1].
    3. If GL_MAP_COLOR is TRUE, glColorSubTableEXT scales each color component by the size of lookup table GL_PIXEL_MAP_c_TO_c, then replaces the component by the value that it references in that table; c is R, G, B, or A, respectively.

    4. The glColorSubTableEXT function converts the resulting RGBA colors to fragments by attaching the current raster position z-coordinate and texture coordinates to each pixel, then assigning x and y window coordinates to the nth fragment such that

      xn = xr + n mod width

      yn = yr + n/width

      where (xr, yr) is the current raster position.

    5. These pixel fragments are then treated just like the fragments generated by rasterizing points, lines, or polygons. The glColorSubTableEXT function applies texture mapping, fog, and all the fragment operations before writing the fragments to the framebuffer.
    GL_RED Each pixel is a single red component.

    The glColorSubTableEXT function converts this component to the internal format in the same way that the red component of an RGBA pixel is, then converts it to an RGBA pixel with green and blue set to 0.0, and alpha set to 1.0. After this conversion, the pixel is treated just as if it had been read as an RGBA pixel.
    GL_GREEN Each pixel is a single green component.

    The glColorSubTableEXT function converts this component to the internal format in the same way that the green component of an RGBA pixel is, and then converts it to an RGBA pixel with red and blue set to 0.0, and alpha set to 1.0. After this conversion, the pixel is treated just as if it had been read as an RGBA pixel.
    GL_BLUE Each pixel is a single blue component.

    The glColorSubTableEXT function converts this component to the internal format in the same way that the blue component of an RGBA pixel is, and then converts it to an RGBA pixel with red and green set to 0.0, and alpha set to 1.0. After this conversion, the pixel is treated just as if it had been read as an RGBA pixel.
    GL_ALPHA Each pixel is a single alpha component.

    The glColorSubTableEXT function converts this component to the internal format in the same way that the alpha component of an RGBA pixel is, and then converts it to an RGBA pixel with red, green, and blue set to 0.0. After this conversion, the pixel is treated just as if it had been read as an RGBA pixel.
    GL_RGB Each pixel is a group of three components in this order: red, green, blue.

    The glColorSubTableEXT function converts each component to the internal format in the same way that the red, green, and blue components of an RGBA pixel are. The color triple is converted to an RGBA pixel with alpha set to 1.0. After this conversion, the pixel is treated just as if it had been read as an RGBA pixel.
    GL_BGR_EXT Each pixel is a group of three components in this order: blue, green, red.

    GL_BGR_EXT provides a format that matches the memory layout of Windows device-independent bitmaps (DIBs). Thus your applications can use the same data with Win32 function calls and OpenGL pixel function calls.
    GL_BGRA_EXT Each pixel is a group of four components in this order: blue, green, red, alpha.

    GL_BGRA_EXT provides a format that matches the memory layout of Windows device-independent bitmaps (DIBs). Thus your applications can use the same data with Win32 function calls and OpenGL pixel function calls.

  • type
    The data type for data. The following symbolic constants are accepted: GL_UNSIGNED_BYTE, GL_BYTE, GL_UNSIGNED_SHORT, GL_SHORT, GL_UNSIGNED_INT, GL_INT, and GL_FLOAT.

    The following table summarizes the meaning of the valid constants for the type parameter.

    Constant Meaning
    GL_UNSIGNED_BYTE Unsigned 8-bit integer
    GL_BYTE Signed 8-bit integer
    GL_UNSIGNED_SHORT Unsigned 16-bit integer
    GL_SHORT Signed 16-bit integer
    GL_UNSIGNED_INT Unsigned 32-bit integer
    GL_INT 32-bit integer
    GL_FLOAT Single-precision floating-point value

  • data
    A pointer to the paletted texture data. The data is treated as single pixels of a 1-D texture palette entry for a palette entry.

Remarks

The glColorSubTableEXT function specifies portions of the current targeted texture's palette to be replaced. Unlike glColorTableEXT, you cannot specify the target parameter to be a proxy texture palette.

Note  The glColorSubTableEXT function is an extension function that is not part of the standard OpenGL library but is part of the GL_EXT_paletted_texture extension. To check whether your implementation of OpenGL supports glColorSubTableEXT, call glGetString(GL_EXTENSIONS). If it returns GL_EXT_paletted_texture, glColorSubTableEXT is supported. To obtain the function address of an extension function, call wglGetProcAddress.

Error Codes

The following are the error codes generated and their conditions.

Error code Condition
GL_INVALID_VALUE start or count was an invalid integer.
GL_INVALID_ENUM target, format, or type was not an accepted value.
GL_INVALID_OPERATION glColorSubTableEXT was called between glBegin and glEnd pairs.

Requirements

**  Windows NT/2000:** Requires Windows NT 4.0 or later.
**  Windows 95/98:** Requires Windows 95 or later. Available as a redistributable for Windows 95.
**  Header:** Declared in Gl.h.
**  Library:** Use Opengl32.lib.

See Also

glBegin, glColorTableEXT, glEnd, glGetColorTableEXT, glGetColorTableParameterfvEXT, glGetColorTableParameterivEXT, glGetString, wglGetProcAddress