bug#39736: 27.0.60; wrong display of scaled checkerd pattern image

bug#39736: 27.0.60; wrong display of scaled checkerd pattern image

[ynyaaa]

A scaled checkered pattern image is converted into a solid gray image.
I expect a large chechered pattern.
Evaluating the form below, a solid gray square is displayed.

(let ((data "\
P1
8 8
01010101
10101010
01010101
10101010
01010101
10101010
01010101
10101010
"))
  (insert-image (create-image data 'pbm t :scale 8)))

The form below temporally displays another image.
The upper side is gray, the lower-left corner is black,
and the lower-right corner is white.
Once the text cursor gets on the image, the whole image is displayed as
a gray square.

(let ((data "P1\n2 2\n01\n10")
      (buf (generate-new-buffer "tmp")))
  (switch-to-buffer buf)
  (insert "\na")
  (goto-char (point-min))
  (redisplay)
  (insert-image (create-image data 'pbm t :scale 16)))


In GNU Emacs 27.0.60 (build 1, x86_64-w64-mingw32)
 of 2019-12-29 built on CIRROCUMULUS
Repository revision: 21c3020fcec0a32122d2680a391864a75393031b
Repository branch: emacs-27
Windowing system distributor 'Microsoft Corp.', version 10.0.18363
System Description: Microsoft Windows 10 Pro (v10.0.1909.18363.657)

Recent messages:

Configured using:
 'configure --without-dbus --host=x86_64-w64-mingw32
 --without-compress-install -C 'CFLAGS=-O2 -static -g3''

Configured features:
XPM JPEG TIFF GIF PNG RSVG SOUND NOTIFY W32NOTIFY ACL GNUTLS LIBXML2
HARFBUZZ ZLIB TOOLKIT_SCROLL_BARS MODULES THREADS PDUMPER LCMS2 GMP

Important settings:
  value of $LANG: JPN
  locale-coding-system: cp932

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
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mm-util mail-prsvr mail-utils term/bobcat help-fns radix-tree cl-print
debug backtrace help-mode easymenu find-func cl-loaddefs cl-lib
japan-util tooltip eldoc electric uniquify ediff-hook vc-hooks
lisp-float-type mwheel dos-w32 ls-lisp disp-table term/w32-win w32-win
w32-vars term/common-win tool-bar dnd fontset image regexp-opt fringe
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prog-mode register page tab-bar menu-bar rfn-eshadow isearch timer
select scroll-bar mouse jit-lock font-lock syntax facemenu font-core
term/tty-colors frame minibuffer cl-generic cham georgian utf-8-lang
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cp51932 hebrew greek romanian slovak czech european ethiopic indian
cyrillic chinese composite charscript charprop case-table epa-hook
jka-cmpr-hook help simple abbrev obarray cl-preloaded nadvice loaddefs
button faces cus-face macroexp files text-properties overlay sha1 md5
base64 format env code-pages mule custom widget hashtable-print-readable
backquote threads w32notify w32 lcms2 multi-tty make-network-process
emacs)

Memory information:
((conses 16 69135 12815)
 (symbols 48 7851 5)
 (strings 32 22941 1828)
 (string-bytes 1 729921)
 (vectors 16 15072)
 (vector-slots 8 259276 24684)
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bug#39736: 27.0.60; wrong display of scaled checkerd pattern image

[Alan Third]

On Sat, Feb 22, 2020 at 11:26:54PM +0900, ynyaaa@gmail.com wrote:
> 
> A scaled checkered pattern image is converted into a solid gray image.
> I expect a large chechered pattern.
> Evaluating the form below, a solid gray square is displayed.
> 
> (let ((data "\
> P1
> 8 8
> 01010101
> 10101010
> 01010101
> 10101010
> 01010101
> 10101010
> 01010101
> 10101010
> "))
>   (insert-image (create-image data 'pbm t :scale 8)))

I believe this is the same as bug#38394. Could you perhaps try the
patch at

    https://debbugs.gnu.org/cgi/bugreport.cgi?bug=38394

> The form below temporally displays another image.
> The upper side is gray, the lower-left corner is black,
> and the lower-right corner is white.
> Once the text cursor gets on the image, the whole image is displayed as
> a gray square.
> 
> (let ((data "P1\n2 2\n01\n10")
>       (buf (generate-new-buffer "tmp")))
>   (switch-to-buffer buf)
>   (insert "\na")
>   (goto-char (point-min))
>   (redisplay)
>   (insert-image (create-image data 'pbm t :scale 16)))

I tried this and couldn’t replicate it, but I believe I had the patch
for 38394 applied, so it may be a fix. Alternatively it could be
related to the way the cursor is drawn on images.
-- 
Alan Third

bug#39736: 27.0.60; wrong display of scaled checkerd pattern image

[Eli Zaretskii]

> Date: Mon, 24 Feb 2020 20:05:23 +0100 (CET)
> From: Alan Third <alan@idiocy.org>
> Cc: 39736@debbugs.gnu.org
> 
> > Evaluating the form below, a solid gray square is displayed.
> > 
> > (let ((data "\
> > P1
> > 8 8
> > 01010101
> > 10101010
> > 01010101
> > 10101010
> > 01010101
> > 10101010
> > 01010101
> > 10101010
> > "))
> >   (insert-image (create-image data 'pbm t :scale 8)))
> 
> I believe this is the same as bug#38394. Could you perhaps try the
> patch at
> 
>     https://debbugs.gnu.org/cgi/bugreport.cgi?bug=38394

The OP is on MS-Windows, and the patch is for XRender configurations,
so it won't help, I think.

> > The form below temporally displays another image.
> > The upper side is gray, the lower-left corner is black,
> > and the lower-right corner is white.
> > Once the text cursor gets on the image, the whole image is displayed as
> > a gray square.
> > 
> > (let ((data "P1\n2 2\n01\n10")
> >       (buf (generate-new-buffer "tmp")))
> >   (switch-to-buffer buf)
> >   (insert "\na")
> >   (goto-char (point-min))
> >   (redisplay)
> >   (insert-image (create-image data 'pbm t :scale 16)))
> 
> I tried this and couldn’t replicate it, but I believe I had the patch
> for 38394 applied, so it may be a fix. Alternatively it could be
> related to the way the cursor is drawn on images.

I didn't see any temporary display, either, FWIW.

bug#39736: 27.0.60; wrong display of scaled checkerd pattern image

[Alan Third]

On Mon, Feb 24, 2020 at 09:24:31PM +0200, Eli Zaretskii wrote:
> > Date: Mon, 24 Feb 2020 20:05:23 +0100 (CET)
> > From: Alan Third <alan@idiocy.org>
> > Cc: 39736@debbugs.gnu.org
> > 
> > > Evaluating the form below, a solid gray square is displayed.
> > > 
> > > (let ((data "\
> > > P1
> > > 8 8
> > > 01010101
> > > 10101010
> > > 01010101
> > > 10101010
> > > 01010101
> > > 10101010
> > > 01010101
> > > 10101010
> > > "))
> > >   (insert-image (create-image data 'pbm t :scale 8)))
> > 
> > I believe this is the same as bug#38394. Could you perhaps try the
> > patch at
> > 
> >     https://debbugs.gnu.org/cgi/bugreport.cgi?bug=38394
> 
> The OP is on MS-Windows, and the patch is for XRender configurations,
> so it won't help, I think.

Ah, I missed that. Thanks for pointing it out.

The problem is likely something similar, though, where there’s some
sort of filtering going on, which is definitely wanted when scaling
the image down, but is less welcome when scaling up.
-- 
Alan Third

bug#39736: 27.0.60; wrong display of scaled checkerd pattern image

[ynyaaa]

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Eli Zaretskii <eliz@gnu.org> writes:

>> > The form below temporally displays another image.
>> > The upper side is gray, the lower-left corner is black,
>> > and the lower-right corner is white.
>> > Once the text cursor gets on the image, the whole image is displayed as
>> > a gray square.
>> > 
>> > (let ((data "P1\n2 2\n01\n10")
>> >       (buf (generate-new-buffer "tmp")))
>> >   (switch-to-buffer buf)
>> >   (insert "\na")
>> >   (goto-char (point-min))
>> >   (redisplay)
>> >   (insert-image (create-image data 'pbm t :scale 16)))
>> 
>> I tried this and couldn’t replicate it, but I believe I had the patch
>> for 38394 applied, so it may be a fix. Alternatively it could be
>> related to the way the cursor is drawn on images.
>
> I didn't see any temporary display, either, FWIW.

I tested with various :scale values.

(let* ((data "P1\n2 2\n01\n10")
       (buf (generate-new-buffer "tmp"))
       (max (1+ (frame-char-height)))
       (scale 4))
  (switch-to-buffer buf)
  (while (<= scale max)
    (erase-buffer)
    (insert (format "\nscale: %g" scale))
    (goto-char (point-min))
    (redisplay)
    (insert-image (create-image data 'pbm t :scale scale))
    (insert ?_)
    (sit-for 0.5)
    (setq scale (1+ scale))))

It seems that if the image is partially displayed under '_',
lower area is painted black and white.
And the maximum value which causes temporary display seems to be
(frame-char-height).

For example, just started after emacs -Q, (frame-char-height) is 16
and :scale 17 simply displays solid gray square.
After (set-frame-font "Courier New-18"), (frame-char-height) is 27
and :scale 28 simply displays solid gray square.

The attached image shows how the square image id displayed.


[-- Attachment #2: emacs-tmp2.png --]
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