Hi,
I'm back from vacation and continuing my exploration of ltk. I'm
currently trying to build a color picker and I'm modeling it after the
blender color picker. To replicate how it looks I need a nice gradient.
My first instinct was to just put a bunch of really small rectangles
(pixels) on a canvas. This worked (see attachment), but it took about 5
minutes for all the pixels to be put on the canvas. Not ideal,
especially if I have to redraw the gradient when the brightness value is
changed by some slider or something. My next idea was to use a bitmap.
This leads my to my first question: How do I get a bitmap on a canvas? I
tried the following code.
```
(defvar image (open "lena_gray.bmp"))
(with-ltk ()
(let* ((canvas (make-instance 'canvas
:width 400
:height 400)))
(pack canvas)
(let ((lena (create-bitmap canvas 20 20 :bitmap image)))
(declare (ignore lena)))))
```
And I get a generic type-error:
The value
NIL
is not of type
STREAM
when binding STREAM
[Condition of type TYPE-ERROR]The value
NIL
is not of type
STREAM
when binding STREAM
[Condition of type TYPE-ERROR]
There is really no example given in the documentation. So I need help
with this one (Using SBCL on Linux by the way).
The next question is concerning transparent colors. To darken the
gradient I thought of having an oval over the bitmap, on which I can
change the transparency value. I haven't found a way to do that with
"itemconfigure". And I also haven't found a place where all the keyword
arguments are listed for "itemconfigure". I'm almost certain that there
are no transparency options for canvas items in tcl/tk. But in case I've
overlooked them, I'm asking anyway.
I'd also like to say that I accept tips on my approach. Is there an
obvious solution that I'm missing or are there other general tips I need
to figure it out myself. Please let me know! Thanks in advance for any help.
Greetings, Tom.
