%
% o region: read the metacontent from this region of the image.
%
-% o length: write the metacontent to this region of the image.
+% o length: the length in bytes of the metacontent.
%
% o metacontent: read these metacontent from the pixel cache.
%
%
% o region: read the pixels from this region of the image.
%
-% o length: write the pixels to this region of the image.
+% o length: the length in bytes of the pixels.
%
% o pixels: read these pixels from the pixel cache.
%
%
% o region: write the metacontent to this region of the image.
%
-% o length: write the metacontent to this region of the image.
+% o length: the length in bytes of the metacontent.
%
% o metacontent: write these metacontent to the pixel cache.
%
%
% o region: write the pixels to this region of the image.
%
-% o length: write the pixels to this region of the image.
+% o length: the length in bytes of the pixels.
%
% o pixels: write these pixels to the pixel cache.
%