|target||Specifies the target texture. Must be GL_TEXTURE_2D.|
|level||Specifies the level-of-detail number. Level 0 is the base image level. Level n is the nth mipmap reduction image.|
|xoffset||Specifies a texel offset in the x direction within the texture array.|
|yoffset||Specifies a texel offset in the y direction within the texture array.|
|width||Specifies the width of the texture subimage.|
|height||Specifies the height of the texture subimage.|
|format||Specifies the format of the pixel data. The following symbolic values are accepted: GL_COLOR_INDEX, GL_RED, GL_GREEN, GL_BLUE, GL_ALPHA, GL_RGB, GL_RGBA, 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, and GL_FLOAT.|
|pixels||Specifies a pointer to the image data in memory.|
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.
glTexSubImage2D redefines a contiguous subregion of an existing two-dimensional texture image. The texels referenced by pixels replace the portion of the existing texture array with x indices xoffset and xoffset + width - 1, inclusive, and y indices yoffset and yoffset + height - 1, inclusive. This region may not include any texels outside the range of the texture array as it was originally specified. It is not an error to specify a subtexture with zero width or height, but such a specification has no effect.
glTexSubImage2D is available only if the GL version is 1.1 or greater.
Texturing has no effect in color index mode.
glPixelStore and glPixelTransfer modes affect texture images in exactly the way they affect glDrawPixels.
GL_INVALID_ENUM is generated if target is not GL_TEXTURE_2D.
GL_INVALID_OPERATION is generated if the texture array has not been defined by a previous glTexImage2D operation.
GL_INVALID_VALUE is generated if level is less than 0.
P GL_INVALID_VALUE may be generated if level is greater than log 2max, where max is the returned value of GL_MAX_TEXTURE_SIZE.
GL_INVALID_VALUE is generated if xoffset < -b, (xoffset + width) > (w - b), yoffset < -b, or (yoffset + height) > (h - b). Where w is the GL_TEXTURE_WIDTH, h is the GL_TEXTURE_HEIGHT, and b is the border width of the texture image being modified. Note that w and h include twice the border width.
GL_INVALID_VALUE is generated if width or height is less than 0.
GL_INVALID_ENUM is generated if format is not an accepted format constant.
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_OPERATION is generated if glTexSubImage2D is executed between the execution of glBegin and the corresponding execution of glEnd.
glIsEnabled with argument GL_TEXTURE_2D
glCopyTexImage1D, glCopyTexImage2D, glCopyTexSubImage1D, glCopyTexSubImage2D, glDrawPixels, glPixelStore, glPixelTransfer, glTexEnv, glTexGen, glTexImage1D, glTexImage2D, glTexSubImage1D, glTexParameter