The glCopyTexSubImage2D function copies a sub-image of a two-dimensional texture image from the frame buffer.
void glCopyTexSubImage2D(
GLenum target,
GLint level,
GLint xoffset,
GLint yoffset,
GLint x,
GLint y,
GLsizei width,
GLsizei height
);
The glCopyTexSubImage2D function replaces a rectangular portion of a two-dimensional texture image with pixels from the current frame buffer, rather than from main memory as is the case for glTexSubImage2D.
A rectangle of pixels beginning with the x and y window coordinates and with the dimensions width and height replaces the portion of the texture array with the indexes xoffset through xoffset + (width – 1), with the indexes yoffset through yoffset + (width – 1) at the mipmap level specified by level. The destination rectangle in the texture array cannot include any texels outside the originally specified texture array.
The glCopyTexSubImage2D function processes the pixels in a row in the same way as glCopyPixels except that before the final conversion of the pixels, all pixel component values are clamped to the range [0, 1] and converted to the texture's internal format for storage in the texture array. Pixel ordering is determined with lower x coordinates corresponding to lower texture coordinates. If any of the pixels within a specified row of the current frame buffer are outside the window associated with the current rendering context, then their values are undefined.
If any of the pixels within the specified rectangle of the current frame buffer are outside the read window associated with the current rendering context, then the values obtained for those pixels are undefined. No change is made to the internalFormat, width, height, or border parameter of the specified texture array or to texel values outside the specified texture sub-image.
You cannot include calls to glCopyTexSubImage2D in display lists.
Note The glCopyTexSubImage2D function is only available in OpenGL version 1.1 or later.
Texturing has no effect in color-index mode. The glPixelStore and glPixelTransfer functions affect texture images in exactly the way they affect the way pixels are drawn using glDrawPixels.
The following functions retrieve information related to glCopyTexSubImage2D:
glIsEnabled with argument GL_TEXTURE_2D.
The following are the error codes generated and their conditions.
| Error Code | Condition |
|---|---|
| GL_INVALID_ENUM | target was not an accepted value. |
| GL_INVALID_VALUE | level was less than zero or greater than log sub 2(max), where max is the returned value of GL_MAX_TEXTURE_SIZE. |
| GL_INVALID_VALUE | xoffset was less than border, (xoffset + width) was greater than (w + border), yoffset was less than border, or (yoffset + height) was greater than (h + border), where w is GL_TEXTURE_WIDTH, h is GL_TEXTURE_HEIGHT, and border is GL_TEXTURE_BORDER. Note that w includes twice the border width. |
| GL_INVALID_VALUE | width was less than border or y was less than border, where border is the border width of the texture array. |
| GL_INVALID_OPERATION | The texture array was not defined by a previous glTexImage2D operation. |
| GL_INVALID_OPERATION | glCopyTexSubImage2D was called between a call to glBegin and the corresponding call to glEnd. |
glBegin, glCopyPixels, glCopyTexSubImage1D, glDrawPixels, glEnd, glFog, glPixelStore, glPixelTransfer, glTexEnv, glTexGen, glTexImage2D, glTexSubImage2D, glTexParameter