Making a colorpicker

[Tom]

Hi,

I did some things, and now it's on Github. Feel free to look: 
https://github.com/Trashtalk217/ltk-colorpicker.

Thanks for the advice I got. I now use two images for displaying the 
color wheel and the white-to-black gradient. While most of the code is 
still yanky as heck (just look at my installation instructions -_-). 
I've managed to create something that works, which I'm very happy with. 
And although the color wheel doesn't become darker when you  turn down 
the brightness, I don't necessarily need it. I can do fine without.

Edgar noted that there's a lisp variable which controls if the Tk code 
gets printed out to standard output, but they didn't know which one it 
was. I found it: (setf *debug-tk* t). I've barely used it because Tk 
hasn't particularly the nicest syntax, but I know where it is if I need it.

Otherwise, thanks again for the help, and I hope you all have a great day.

Greetings, Tom

On 8/15/19 10:41 AM, cage wrote:
> On Wed, Aug 14, 2019 at 08:49:30PM +0200, Tom wrote:
>> Hi,
> Hello!
>
>> I'm back from vacation and continuing my exploration of ltk.
> Hope you had fun! :)
>
>> I'm currently
>> trying to build a color picker
> i think this is  an exercise (and a good one  in my opinion) otherwise
> please consider using:
>
> https://www.tcl.tk/man/tcl8.6/TkCmd/chooseColor.htm
>
>> 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,
> Yes, canvas is slow for these operations.
>
>> 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.
> Please note  that 'bitmap' is  for 1 bit color  depth image (i  e. two
> color)   plus  a   transparency   binary  value,   according  to   the
> documentation:
>
> https://www.tcl.tk/man/tcl8.6/TkCmd/bitmap.htm
>
> Moreover  the format  the library  accepts is  not MS  bitmap but  X11
> bitmap  format, never  used  but likely  these  are the  specification
> (please someone correct if i am wrong):
>
> https://en.wikipedia.org/wiki/X_BitMap
>
> What i think you need is a photo-image:
>
> https://www.tcl.tk/man/tcl8.6/TkCmd/photo.htm
>
> that, instead support 24bit (plus alpha in the upcoming 8.7 release of
> tcl/tk) color depth image.
>
> Tk supports only PNG and GIF format (you can write your own loader but
> this is a more complicate task, so i will stick to PNG here):
>
> (with-ltk ()
>    (let ((canvas (make-canvas nil :width 64 :height 64))
>          (image  (make-image)))
>      (image-load image "/path/to/a/file/in/png/format.png")
>      (create-image canvas 0 0 :image image)
>      (pack canvas)))
>
>> 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 suggest to look at the ltk sources and the official tk documentation.
>
> https://www.tcl.tk/man/tcl8.6/TkCmd/canvas.htm
>
> IIRC usually the options that 'ltk:itemconfigure' accepts are the same that
> 'ltk:create-*' accepts.
>
>> 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.
> As far as i know there is  not an alpha channel but probably you could
> just do  the calculation for  transparency value outside and  draw the
> oval with the results  color (in this case could be  useful to look at
> ltk:image-setpixel); this, also,  could be a tedious  and complex task
> to accomplish, though.
>
>> 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.
> Well the best i can suggest is to take a look here :-)
>
> https://github.com/VitoVan/cl-pkr
>
> Bye, and happy hacking! :)
>
> C.
>
> PS: annoying legal stuff: all my code in this message is released under MIT license
>      https://opensource.org/licenses/MIT
>