glTexSubImage2D function

Artikkel
12/11/2020

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
GL_INVALID_ENUM	target was not GL_TEXTURE_2D.
GL_INVALID_ENUM	format was not an accepted constant.
GL_INVALID_ENUM	type was not an accepted constant.
GL_INVALID_ENUM	type was GL_BITMAP and format was not GL_COLOR_INDEX.
GL_INVALID_VALUE	level was less than zero or greater than log2 max, where max was the returned value of GL_MAX_TEXTURE_SIZE.
GL_INVALID_VALUE	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.
GL_INVALID_VALUE	width was less than b, where b is the border width of the texture array.
GL_INVALID_VALUE	border was not zero or 1.
GL_INVALID_OPERATION	The texture array was not defined by a previous glTexImage2D operation.
GL_INVALID_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:

glGetTexImage

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	Gl.h
Library	Opengl32.lib
DLL	Opengl32.dll

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