glCopyTexImage2D - copy pixels into a 2D texture image
void glCopyTexImage2D(GLenum target, GLint level, GLenum internalformat, GLint x, GLint y, GLsizei width, GLsizei height, GLint border);
glCopyTexImage2D defines a two-dimensional texture image, or cube-map texture image with pixels from the current GL_READ_BUFFER.
The screen-aligned pixel rectangle with lower left corner at (x, y) and with a width of width + 2 border and a height of height + 2 border defines the texture array at the mipmap level specified by level. internalformat specifies the internal format of the texture array.
The pixels in the rectangle are processed exactly as if glReadPixels() had been called, but the process stops just before final conversion. At this point all pixel component values are clamped to the range 0 1 and then converted to the texture's internal format for storage in the texel array.
Pixel ordering is such that lower x and y screen coordinates correspond to lower s and t texture coordinates.
If any of the pixels within the specified rectangle of the current GL_READ_BUFFER are outside the window associated with the current rendering context, then the values obtained for those pixels are undefined.
When internalformat is one of the sRGB types, the GL does not automatically convert the source pixels to the sRGB color space. In this case, the glPixelMap function can be used to accomplish the conversion.
1, 2, 3, and 4 are not accepted values for internalformat.
An image with height or width of 0 indicates a NULL texture.
GL_INVALID_ENUM is generated if target is not GL_TEXTURE_2D, GL_TEXTURE_CUBE_MAP_POSITIVE_X, GL_TEXTURE_CUBE_MAP_NEGATIVE_X, GL_TEXTURE_CUBE_MAP_POSITIVE_Y, GL_TEXTURE_CUBE_MAP_NEGATIVE_Y, GL_TEXTURE_CUBE_MAP_POSITIVE_Z, or GL_TEXTURE_CUBE_MAP_NEGATIVE_Z.
GL_INVALID_VALUE is generated if level is less than 0.
GL_INVALID_VALUE may be generated if level is greater than log 2 max, where max is the returned value of GL_MAX_TEXTURE_SIZE.
GL_INVALID_VALUE is generated if width is less than 0 or greater than GL_MAX_TEXTURE_SIZE.
GL_INVALID_VALUE is generated if non-power-of-two textures are not supported and the width or depth cannot be represented as 2 k + 2 border for some integer k.
GL_INVALID_VALUE is generated if border is not 0 or 1.
GL_INVALID_VALUE is generated if internalformat is not an accepted format.
GL_INVALID_OPERATION is generated if internalformat is GL_DEPTH_COMPONENT, GL_DEPTH_COMPONENT16, GL_DEPTH_COMPONENT24, or GL_DEPTH_COMPONENT32 and there is no depth buffer.
glCopyTexImage1D(), glCopyTexSubImage1D(), glCopyTexSubImage2D(), glPixelStore(), glTexImage1D(), glTexImage2D(), glTexSubImage1D(), glTexSubImage2D(), glTexParameter()
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