When a graphics texture mapping apparatus is to perform a texture filtering operation that uses the data values of a plurality of texels, the texture mapper first determines whether any of the data values of the texels to be used for the texture filtering operation are the same, and then selects a texture filtering operation to be performed using data values of the texels based on the determination. The texture mapper then performs the selected texture filtering operation using one or more of the data values of the texels to provide the required texture filtering operation output result.