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Re: ⎕PNG


From: Christian Robert
Subject: Re: ⎕PNG
Date: Wed, 21 Sep 2022 14:04:17 -0400
User-agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.3.0

There are two comments that start with "/" rather than "//"

Xtian.


Quad_PNG.cc:865:1: error: expected unqualified-id before ‘/’ token
  865 | 
/----------------------------------------------------------------------------
      | ^
Quad_PNG.cc:886:1: error: expected unqualified-id before ‘/’ token
  886 | 
/-----------------------------------------------------------------------------
      | ^
Quad_PNG.cc:51:12: warning: ‘verbosity’ defined but not used [-Wunused-variable]
   51 | static int verbosity = SHOW_NONE;
      |            ^~~~~~~~~
make[3]: *** [Makefile:4374: apl-Quad_PNG.o] Error 1
make[3]: *** Waiting for unfinished jobs....
mv -f .deps/apl-UserPreferences.Tpo .deps/apl-UserPreferences.Po
make[3]: Leaving directory '/home/xtian/gnuapl/src'
make[2]: *** [Makefile:5010: all-recursive] Error 1
make[2]: Leaving directory '/home/xtian/gnuapl/src'
make[1]: *** [Makefile:537: all-recursive] Error 1
make[1]: Leaving directory '/home/xtian/gnuapl'
make: *** [Makefile:425: all] Error 2
[xtian@fedora:/home/xtian/gnuapl] $


On 2022-09-21 07:49, Dr. Jürgen Sauermann wrote:
Hi,

I would like to announce a new GNU APL feature: ⎕PNG

PNG stands for "Portable Network Graphics" and is a file format, standardized
in RFC 2083, for (still) images that is, among several other use cases, also
directly understood by web browsers.

Unlike some of the other image file formats around, the PNG file format
has no strings attached, such as patents or copyrights. This was one of the
reasons for choosing it in GNU APL.

While APL appears to be the perfect choice for manipulating the large pixel
arrays of images, this is not the case for the files on disc from which the 
pixel
arrays are read or eventually stored. ⎕PNG tries to close this gap.

*⎕PNG* is comprised of three simple sub-function for:

1. reading a *.png* file into an APL array of pixels,
2. displaying such an array in a GTK window on the screen, and
3. writing a (supposedly somehow manipulated) pixel array into a *.png* file.

The main work in the conversions above is actually provided by *libpng* (see
www.libpng.org <www.libpng.org>) therefore ⎕PNG is merely a lightweight wrapper 
around
*libpng*. ⎕PNG is supposed to support all file variants (colour and grayscale,
different pixel resolutions from 1 to 16 bits, with or without alpha channel),
on input and most (= all but pixel arrays using colour palettes) on output.

*SVN 1589*, see also i*nfo apl* section 2.32 for details.

Enjoy,
Jürgen






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