On 18/04/2012 10:17, Tamas K Papp wrote:
I would like to write a plotting function that draws image plots
(plotting a matrix in 2d using colors). It would be useful to use
gradients; in particular, paint a rectangle where the four corners each
have a color and the each point in the rectangle has a color which is a
convex combination of the corner colors. I think this is called a
gradient in most libraries, but I could not figure out how to do it in
cl-pdf (I have to admit that I didn't find gradients in the library,
maybe I didn't look hard enough).
Hi,
Gradients of this sort are called shading patterns in PDF (available
from PDF version 1.3). Several types of shading patterns are available:
function-based, axial, radial, Gourad-shaded. cl-pdf doesn't have any
support for this, but it shouldn't be very hard to add.
The PDF specification is available from
http://www.adobe.com/devnet/pdf/pdf_reference_archive.html
You want section 4.6.3.
--
Eric
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