Hi Christoph.

> For a potentially relevant reference implementtion ...
And maybe double-check with the specification: https://www.w3.org/Graphics/GIF/spec-gif89a.txt [https://www.w3.org/Graphics/GIF/spec-gif89a.txt]

Best,
Marcel
Am 09.10.2020 16:15:36 schrieb commits at source.squeak.org <commits at source.squeak.org>:
Christoph Thiede uploaded a new version of Graphics to project The Inbox:
http://source.squeak.org/inbox/Graphics-ct.443.mcz

==================== Summary ====================

Name: Graphics-ct.443
Author: ct
Time: 9 October 2020, 4:15:09.97236 pm
UUID: 897346b7-ceaa-1a43-874f-3571d893309c
Ancestors: Graphics-pre.439

Adds basic support for storing an animated GIF file via AnimatedGIFReadWriter.

Note that this implementation indeed is very rudimentary only. I found several GIF files on my computer that cannot be saved as a GIF correctly (something is wrong with the encoding of the background/alpha color). But on the other hand, I also met a number of GIF files that cannot be read by the AnimatedGIFReadWriter ("error: improper store") ...
For a potentially relevant reference implementtion, I found this one, but I did not yet find the time apply it: https://gist.github.com/JimBobSquarePants/cac72c4e7d9f05f13ac9

Following the idea of "baby steps", I'd like to get this into the Trunk at this early state however. The motivation behind this is that I would like to use this concept from another project so establishing the protocol as soon as possible would be helpful for me to write tests.

=============== Diff against Graphics-pre.439 ===============

Item was added:
+ ----- Method: AnimatedGIFReadWriter class>>exampleAnim (in category 'examples') -----
+ exampleAnim
+ "AnimatedGIFReadWriter exampleAnim"
+
+ | extent center frames |
+ extent := 42 @ 42.
+ center := extent // 2.
+ frames := (2 to: center x - 1 by: 2) collect: [:r |
+ "Make a fancy anim without using Canvas - inefficient as hell"
+ | image |
+ image := ColorForm extent: extent depth: 8.
+ 0.0 to: 359.0 do: [:theta |
+ image
+ colorAt: (center + (Point r: r degrees: theta)) rounded
+ put: Color red].
+ image].
+
+ ^ FileStream newFileNamed: 'anim.gif' do: [:stream |
+ self
+ putForms: frames
+ andDelays: (frames withIndexCollect: [:frame :index |
+ 10 + (index / frames size * 100)]) "Start fast, end slow"
+ onStream: stream]!

Item was added:
+ ----- Method: AnimatedGIFReadWriter class>>putForms:andDelays:onStream: (in category 'image reading/writing') -----
+ putForms: forms andDelays: delays onStream: aWriteStream
+ "Store the given form sequence as an animation on the given stream."
+
+ | writer canvas |
+ self assert: forms size = delays size.
+
+ writer := self on: aWriteStream.
+ canvas := Form extent: forms first extent depth: 32.
+ [Cursor write showWhile: [
+ writer loopCount: -1.
+ forms with: delays do: [:form :delay |
+ writer delay: delay; flag: #todo. "ct: Does not work"
+ form displayOn: canvas at: 0 @ 0 rule: Form over.
+ writer nextPutImage: canvas]]]
+ ensure: [writer close].!

Item was added:
+ ----- Method: AnimatedGIFReadWriter class>>putForms:onFileNamed: (in category 'image reading/writing') -----
+ putForms: formSequence onFileNamed: fileName
+ "Store the given form sequence as an animation on a file of the given name."
+
+ FileStream newFileNamed: fileName do: [:stream |
+ self putForms: formSequence onStream: stream].!

Item was added:
+ ----- Method: AnimatedGIFReadWriter class>>putForms:onStream: (in category 'image reading/writing') -----
+ putForms: forms onStream: aWriteStream
+ "Store the given form sequence as an animation on the given stream."
+
+ ^ self
+ putForms: forms
+ andDelays: ((1 to: forms size) collect: [:i | 20])
+ onStream: aWriteStream!

Item was changed:
----- Method: BMPReadWriter class>>readAllFrom: (in category 'testing') -----
readAllFrom: fd
"MessageTally spyOn:[BMPReadWriter readAllFrom: FileDirectory default]"
fd fileNames do:[:fName|
(fName endsWith: '.bmp') ifTrue:[
+ [Form fromBinaryStream: (fd readOnlyFileNamed: fName)] ifError: [].
- [Form fromBinaryStream: (fd readOnlyFileNamed: fName)] on: Error do:[:nix].
].
].
fd directoryNames do:[:fdName|
self readAllFrom: (fd directoryNamed: fdName)
].!

Item was removed:
- ----- Method: GIFReadWriter class>>exampleAnim (in category 'examples') -----
- exampleAnim
- "GIFReadWriter exampleAnim"
-
- | writer extent center |
- writer := GIFReadWriter on: (FileStream newFileNamed: 'anim.gif').
- writer loopCount: 20. "Repeat 20 times"
- writer delay: 10. "Wait 10/100 seconds"
- extent := 42 at 42.
- center := extent / 2.
- Cursor write showWhile: [
- [2 to: center x - 1 by: 2 do: [:r |
- "Make a fancy anim without using Canvas - inefficient as hell"
- | image |
- image := ColorForm extent: extent depth: 8.
- 0.0 to: 359.0 do: [:theta | image colorAt: (center + (Point r: r degrees: theta)) rounded put: Color red].
- writer nextPutImage: image]
- ] ensure: [writer close]].!


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