Graphics
If users may select colors as an attribute of graphic elements, allow
them to specify colors directly by pointing at displayed samples, rather than
requiring them to name the colors.
Exception: If only a few colors
are available, their names can probably be used reliably.
Comment: If
many colors are available, users with normal vision can choose from displayed
samples more reliably than from a list of color names. For color-blind users,
however, it might be helpful to add names/labels to the displayed samples.
Comment: For more elaborate graphic art, it may be helpful to allow
users to mix their own colors by sequential selection (i.e., cursor placement), either in a displayed palette or directly in a graphic image. Such color mixing could permit user control of saturation, brightness, and opacity/transparency, as well as hues.
During graphic data entry/editing, display the selected
attributes that will affect current actions for ready reference by the user.
Example: When graphic attributes --
plotting symbols, character size, line type, color, etc. -- are chosen from
displayed menus, it might suffice to highlight the currently selected menu
options; alternatively, current selections might be shown in some sort of
"reminder" window.
Example: A few
attributes might be shown by the displayed cursor, i.e., by changing cursor
shape, size or color depending upon current attribute selections.
Example: If rubberbanding is provided to aid line
drawing, then that process itself would show the currently selected line type.
Comment: Users may forget what options have been
chosen. Displayed reminders will be particularly important in situations where
the consequences of a mistaken user action are difficult to reverse, e.g., where
it may be hard to erase a wrongly drawn line.
Comment: In some applications, display cues may not be adequate to
convey attribute information completely.
There may not be sufficient room on the display. Or the attributes
may derive from underlying models whose characteristics are too complex for simple display representation.
In such cases, users should be able to request auxiliary display of such information to determine the operative context for current actions.
When entering or editing graphic data, allow users to change
display attributes -- e.g., line type, cross-hatching, color -- for selected
graphic elements.
Example: If a figure was
created initially with dashed lines, then a user should be able to select the
figure, or portions of it, and change the dashed lines to solid lines by
specifying that alternative attribute.
Comment: If it
is easy to change attributes, reversing earlier data entry decisions, then the
process of composing graphic displays will be generally easier.
Comment: Another approach to changing an attribute might be to rely
on general editing capabilities, i.e., to delete the element in question (perhaps using an UNDO command for an element just created) and then redraw it. But a capability for specifying attribute change directly, without element
deletion and reentry, will often be helpful.
See also:
Selecting Colors