Lossless Optimization of PNG files

[tiagofilipesilva]

BPO	30660
Nosy	@vstinner, @methane, @serhiy-storchaka, @tiagofilipesilva
PRs	bpo-30660: Replaced PNG files with their lossless optimized version #2141 bpo-30660: Doc: Optimize PNG files #8032

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2018-07-01.07:03:26.091>
created_at = <Date 2017-06-13.23:11:28.720>
labels = ['docs', '3.8', 'performance']
title = 'Lossless Optimization of PNG files'
updated_at = <Date 2018-07-01.07:03:26.088>
user = 'https://github.com/tiagofilipesilva'

bugs.python.org fields:

activity = <Date 2018-07-01.07:03:26.088>
actor = 'methane'
assignee = 'docs@python'
closed = True
closed_date = <Date 2018-07-01.07:03:26.091>
closer = 'methane'
components = ['Documentation']
creation = <Date 2017-06-13.23:11:28.720>
creator = 'tfs'
dependencies = []
files = []
hgrepos = []
issue_num = 30660
keywords = ['patch']
message_count = 7.0
messages = ['295969', '295989', '295990', '298375', '320795', '320801', '320826']
nosy_count = 5.0
nosy_names = ['vstinner', 'methane', 'docs@python', 'serhiy.storchaka', 'tfs']
pr_nums = ['2141', '8032']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'resource usage'
url = 'https://bugs.python.org/issue30660'
versions = ['Python 3.8']

[tiagofilipesilva]

I took the liberty to apply tools that optimize the binary weight (without loss of quality) of the 14 PNG files present in the Python 3.7 source tree and then applied a pull request (bpo-2141).

Is there anything to be discussed? Thanks.

[serhiy-storchaka]

What tools did you use, optipng, advpng, pngcrush, pngnq, pngquant, or other? How much space is saved?

Note that some tools remove an information about palette that makes files displaying differently on different platforms and output devises.

[vstinner]

I suggest to work on Sphinx to propose to implement this optimization on the HTML rendering, maybe with optional external tools. What do you think?

Another attempt: bpo-27461 :-)

[tiagofilipesilva]

Sorry for the late reply. I had to deal with stuff.

serhiy.storchaka:

What tools did you use, optipng, advpng, pngcrush, pngnq, pngquant, or other? How much space is saved?

I had half a crate of whiskey that day so I'm going to say optipng and pngcrush were used and if my recollection is good the saved space was ≈ 5 to 50 % depending on the file.

Note that some tools remove an information about palette that makes files displaying differently on different platforms and output devises.

I am aware of that. But if I understood correctly these files are rendered in documentation, and I don't think they're going to do this in a PlayStation 2. There may be complaints with Windows XP users because I remember for sure that optimized PNG files could not render very well back in those days.

haypo:

I suggest to work on Sphinx to propose to implement this optimization on the HTML rendering, maybe with optional external tools. What do you think?

Like you I'm very fond of a long-term proper solution and that is, by the way, the solution you deserve.

Unfortunately, I do not have the skills for provide that. I can only give the solution you need (which is smaller files).

[methane]

It seems PR author removed his repository and the PR can't be merge via conflict.

In master branch:

02:18 $ ll **/.png
-rw-r--r-- 1 inada-n staff 3732 7 1 02:13 faq/python-video-icon.png
-rwxr-xr-x 1 inada-n staff 49648 7 1 02:09 howto/logging_flow.png
-rw-r--r-- 1 inada-n staff 24719 7 1 02:09 library/depgraph-output.png
-rw-r--r-- 1 inada-n staff 11148 7 1 02:09 library/hashlib-blake2-tree.png
-rw-r--r-- 1 inada-n staff 11280 7 1 02:09 library/pathlib-inheritance.png
-rw-r--r-- 1 inada-n staff 45021 7 1 02:09 library/tulip_coro.png
-rw-r--r-- 1 inada-n staff 39585 7 1 02:09 library/turtle-star.png
-rw-r--r-- 1 inada-n staff 48994 7 1 02:13 using/win_installer.png

In lossless_png branch:

$ ll **/*.png
-rw-r--r--  1 inada-n  staff   2791  7  1 02:28 faq/python-video-icon.png
-rwxr-xr-x  1 inada-n  staff  19351  7  1 02:28 howto/logging_flow.png*
-rw-r--r--  1 inada-n  staff  11158  7  1 02:28 library/depgraph-output.png
-rw-r--r--  1 inada-n  staff  10590  7  1 02:28 library/hashlib-blake2-tree.png
-rw-r--r--  1 inada-n  staff   6168  7  1 02:28 library/pathlib-inheritance.png
-rw-r--r--  1 inada-n  staff  33565  7  1 02:28 library/tulip_coro.png
-rw-r--r--  1 inada-n  staff  29964  7  1 02:28 library/turtle-star.png
-rw-r--r--  1 inada-n  staff  37942  7  1 02:28 using/win_installer.png

[methane]

03:19 $ find . -name '*.png' | xargs optipng -o7
03:20 $ ll **/*.png
-rw-r--r-- 1 inada-n staff 2888 7 1 03:20 faq/python-video-icon.png
-rw-r--r-- 1 inada-n staff 22058 7 1 03:20 howto/logging_flow.png
-rw-r--r-- 1 inada-n staff 11146 7 1 03:20 library/hashlib-blake2-tree.png
-rw-r--r-- 1 inada-n staff 6456 7 1 03:20 library/pathlib-inheritance.png
-rw-r--r-- 1 inada-n staff 36812 7 1 03:20 library/tulip_coro.png
-rw-r--r-- 1 inada-n staff 33808 7 1 03:20 library/turtle-star.png
-rw-r--r-- 1 inada-n staff 42117 7 1 03:20 using/win_installer.png

While this output is bigger than PR-2141, I think it's good enough.

[methane]

New changeset c6cd164 by INADA Naoki in branch 'master':
bpo-30660: Doc: Optimize PNG files by optipng (GH-8032)
c6cd164