Re: [MACTCL] Partial PNG transparency not working in Cocoa Tk

[Wojciech K. <woj...@ko...>]

Hi,

I have recently noticed it myself and done some investigation on the
issue. Here is some summary:

- happens on OS X 10.9 only - does not happen on 10.8 and below (also,
transparency works fine on all other systems and all other OS X
versions, so I suspect this is a change in OS X 10.9 that broke it)

- happens with latest Tcl/Tk from fossil, latest ActiveTcl

- happens with both tkpng and Img

- I can also confirm it only happens with Cocoa, not Carbon

So this is definitely an issue with Tk.

As I am not a Cocoa/Tk expert, that is as far as I went. For the
affected code I simply created PNG images with 0%/100% transparency
and use transparent images for other OSes for now, at least until this
is resolved.


2013/11/29 Linus Nyberg <li...@fa...>:
> Hi all,
>
> I’m trying to move our application over from Carbon based Tcl/Tk (8.5.4) to
> any of the Cocoa versions (8.5.13 or 8.6.1) in order to get Retina text, 64
> bit support, future proof, etc.
> One show stopper problem I’m having is that tk “images” don’t seem to render
> partial transparency (where pixels are 1-99% transparent).
> Here’s a screenshot of the result I get, where I show a “label -image”, a
> “label -bitmap” and “canvas image” with the same transparent png image. Only
> the bitmap label works, the others are wrong:
> https://dl.dropboxusercontent.com/u/12145205/alphatest_fail.png
>
> Does anyone have any tips on how to get this working? It works fine on the
> old Carbon based Tk, using the tkpng extension. It also works fine on 8.6.1
> on *Windows*.
> I wish it was as easy as just using “-bitmap” based labels all the time, but
> we at least really need images to work in canvas as well (bitmap does not
> work there as far as I know).
>
> Here are replication steps:
> - Download and install ActiveTcl 8.6.1
> - Go to http://www.w3.org/Graphics/PNG/inline-alpha.html and drag the test
> png image to your Desktop
> - Save the code below to a file (for example “alphatest.tcl on your
> desktop).
> - Open Wish.app for Tcl 8.6.1 and “Source…” alphatest.tcl
> - Happens: The image based label and image in canvas are wrong, but the
> bitmap based label works.
>
> # alphatest.tcl
> #-----------------
> set png_path "~/Desktop/alphatest.png"
>
> wm geometry . 400x900
>
> ::tk::mac::iconBitmap test_png 380 287 -imageFile $png_path
> image create photo test_png -format png -width 380 -height 287 -file
> $png_path
>
> # LABEL BASED ON "image" - does not handle partial transparency well
> #-----------------------
> set l .image_label
> label $l -image test_png
> place $l -x 10 -y 10 -anchor nw
>
> # LABEL BASED ON "bitmap" - works
> #-----------------------
> set l2 .bitmap_label
> label $l2 -bitmap test_png
> place $l2 -x 10 -y 300 -anchor nw
>
> # IMAGE IN CANVAS (BASED ON "image") - does not handle partial transparency
> well
> #-----------------------------------
> set c .c
> canvas $c -width 500 -height 310 -bg white
> place $c -x 10 -y 600 -anchor nw
> $c create image 10 10 -image test_png -anchor nw
>
>
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