Returns the overall width of the image in pixels, for the given (image) resolution level. This is the image's width without accounting for any component subsampling or tiling.

       <p>Note: Image resolution level indexes may differ from tile-component
       resolution index. They are indeed indexed starting from the lowest
       number of decomposition levels of each component of each tile.</p><p>Example: For an image (1 tile) with 2 components (component 0 having
       2 decomposition levels and component 1 having 3 decomposition levels),
       the first (tile-) component has 3 resolution levels and the second one
       has 4 resolution levels, whereas the image has only 3 resolution levels
       available.</p>