[cl-gd-devel] Re: Drawing anti-aliased text with transparent background

18 Mar 2007


      I got some help from libgd mailing list, so when I put Pierre's sample to
lisp here is what I got (solves my problem):

    (with-image (new width height t)
      (setf (alpha-blending-p new) nil)
      (draw-rectangle* 0 0 width height :image new :filled t :color
(allocate-color 0 0 0 :image new :alpha 127))
      (draw-freetype-string 0 0
                text
                :image new
                :anti-aliased t
                :font-name font
                :angle 0
                :point-size font-size
                :color (allocate-color 0 0 255 :image new))
      (setf (save-alpha-p :image new) t)
      (write-image-to-file file-name :image new :if-exists :supersede)))

Thank you,
Andrew

On 3/17/07, Andrei Stebakov <lispercat@gmail.com> wrote:
...
Ah, it looks like make-anti-aliased is only for brushes, for drawing
lines... I wonder what technique works for the text?
Thanks!
Andrew
On 3/17/07, Andrei Stebakov <lispercat@gmail.com> wrote:
...
I tred to use the (make-anti-aliased) function:
    (draw-freetype-string 0 0
                  text
                  :anti-aliased t
                  :font-name font
                  :angle 0
                  :point-size font-size
                  :color (make-anti-aliased (allocate-color 0 0 255)))
But the lisp gives me the error:
The value of CL-GD::COLOR is #S(CL-GD::ANTI-ALIASED-COLOR
                                  :COLOR 255
                                  :DO-NOT-BLEND NIL), which is not of
type INTEGER.
   [Condition of type SIMPLE-TYPE-ERROR]
Restarts:
 0: [STORE-VALUE] Supply a new value of CL-GD::COLOR.
 1: [ABORT] Return to SLIME's top level.
 2: [ABORT] Return to Top-Level.
Backtrace:
  0: (LISP::CHECK-TYPE-ERROR CL-GD::COLOR
                             #S(CL-GD::ANTI-ALIASED-COLOR
                                  :COLOR 255
                                  :DO-NOT-BLEND NIL)
                             INTEGER
                             NIL)
Thank you,
Andrew
On 3/17/07, Andrei Stebakov < lispercat@gmail.com> wrote:
...
Here is what I've got:
http://www.greenpixeldesign.com/cphandler/tmp-img/test.png
I'd like to remove the black outline from the anti-aliased text (I
need RGB true color image). I know I am missing some stupid thing, but I
experimented with different backgrounds, just doesn't make it right. My
current setup is gdlib 2.0.33 on debian, and here is the code;
(defun create-text-image (text font font-size file-name)
  (multiple-value-bind (width height horizont-shift vertical-shift)
      (get-bounding-rect text font font-size)
    (with-image* (width height t)
      (let* ((white (allocate-color 255 255 255))
         (black (allocate-color 0 0 0))
         (red (allocate-color 255 0 0))
         (green (allocate-color 0 255 0))
         (blue (allocate-color 0 0 255)))
    (setf (transparent-color) black)
    (draw-freetype-string (- 0 horizont-shift) (- height
vertical-shift)
                  text
                  :anti-aliased t
                  :font-name font
                  :angle 0
                  :point-size font-size
                  :color (allocate-color 0 0 255))
;;(true-color-to-palette)
    (write-image-to-file file-name :if-exists :supersede)))))