Adds an underline and blue color. The pict’s height and descent are extended.
Scales a color, making it brighter or darker. If the factor is less than 1, the color is darkened by multiplying the RGB components by the factor. If the factor is greater tham 1, the color is lightened by dividing the gap between the RGB components and 255 by the factor.
|dc : (is-a?/c dc<%>)|
|max-step : exact-nonnegative-integer?|
|step-delta : (and/c exact? positive?)|
|start : (or/c string? (is-a?/c color%))|
|end : (or/c string? (is-a?/c color%))|
|proc : (exact? . -> . any)|
|set-pen? : any/c|
|set-brush? : any/c|
Calls a proc multiple times, gradually changing the pen and/or brush color for each call. For the first call, the current pen and/or brush color matches start; for the last call, it matches racket[end]; and for intermediate calls, the color is an intermediate color.
The max-step and step-delta arguments should be exact numbers; the procedure is called with each number from 0 to max-step inclusive using a step-delta increment.