glTexSubImage2D function
The glTexSubImage2D function specifies a portion of an existing one-dimensional texture image. You cannot define a new texture with glTexSubImage2D.
Syntax
void WINAPI glTexSubImage2D(
GLenum target,
GLint level,
GLint xoffset,
GLint yoffset,
GLsizei width,
GLsizei height,
GLenum format,
GLenum type,
const GLvoid *pixels
);
Parameters
-
target
-
The target texture. Must be GL_TEXTURE_2D.
-
level
-
The level-of-detail number. Level 0 is the base image. Level n is the nth mipmap reduction image.
-
xoffset
-
A texel offset in the x direction within the texture array.
-
yoffset
-
A texel offset in the y direction within the texture array.
-
width
-
The width of the texture sub-image.
-
height
-
The height of the texture sub-image.
-
format
-
The format of the pixel data. It can assume one of the following symbolic values.
Value Meaning - GL_COLOR_INDEX
Each element is a single value, a color index. It is converted to fixed point format (with an unspecified number of 0 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. It is converted to floating point format and assembled into an RGBA element by attaching 0.0 for green and blue, and 1.0 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. It is converted to floating point format and assembled into an RGBA element by attaching 0.0 for red and blue, and 1.0 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. It is converted to floating point format and assembled into an RGBA element by attaching 0.0 for red and green, and 1.0 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. It is converted to floating point format and assembled into an RGBA element by attaching 0.0 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
Each element is an RGB triple. It is converted to floating point format and assembled into an RGBA element by attaching 1.0 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
Each element is a complete RGBA element. It is converted to floating point. 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
Each element is a single luminance value. It is converted to floating point format, and then assembled into an RGBA element by replicating the luminance value three times for red, green, and blue, and attaching 1.0 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. It is converted to floating point format, and then assembled 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). -
type
-
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, and GL_FLOAT.
-
pixels
-
A pointer to the image data in memory.
Return value
This function does not return a value.
Error codes
The following error codes can be retrieved by the glGetError function.
| Name | Meaning |
|---|---|
|
target was not GL_TEXTURE_2D. |
|
format was not an accepted constant. |
|
type was not an accepted constant. |
|
type was GL_BITMAP and format was not GL_COLOR_INDEX. |
|
level was less than zero or greater than log2 max, where max was the returned value of GL_MAX_TEXTURE_SIZE. |
|
xoffset was less than -b; or xoffset + width was greater than w - b; or yoffset was less than -b; or yoffset + height was greater than h - b, where w is the GL_TEXTURE_WIDTH, h is the GL_TEXTURE_HEIGHT, and b is the width of the GL_TEXTURE_BORDER of the texture image being modified. Note that w and h include twice the border width. |
|
width was less than b, where b is the border width of the texture array. |
|
border was not zero or 1. |
|
The texture array was not defined by a previous glTexImage2D operation. |
|
The function was called between a call to glBegin and the corresponding call to glEnd. |
Remarks
Two-dimensional texturing for a primitive is enabled using glEnable and glDisable with the argument GL_TEXTURE_2D. During texturing, part of a specified texture image is mapped into each enabled primitive. You use the glTexSubImage2D function to specify a contiguous sub-image of an existing two-dimensional texture image for texturing.
The texels referenced by pixels replace a region of the existing texture array with x indexes of xoffset and xoffset + (width 1) inclusive and y indexes of yoffset and yoffset + (height 1) inclusive. This region cannot include any texels outside the range of the originally specified texture array.
Specifying a sub-image with a width of zero has no effect and does not generate an error.
Texturing has no effect in color-index mode.
In general, texture images 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. The glPixelStore and glPixelTransfer modes affect texture images in exactly the way they affect glDrawPixels.
The following functions retrieve information related to glTexSubImage2D:
glIsEnabled with argument GL_TEXTURE_2D
Requirements
| Requirement | Value |
|---|---|
| Minimum supported client |
Windows 2000 Professional [desktop apps only] |
| Minimum supported server |
Windows 2000 Server [desktop apps only] |
| Header |
|
| Library |
|
| DLL |
|
See also
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