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paint/README.md

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+# Piecasso — A desktop Paint application in PyQt
+
+Express yourself with PieCasso, the only painting programme to feature
+ready made pictures of pie.
+
+Piecasso is a clone of the Paint programme from Windows 95 (ish) with a
+few additions (and subtractions). The programme features standard
+tools including pen, brush, fill, spray can, eraser, text and a number of
+shape drawing widgets. 
+
+![Piecasso](screenshot-paint.png)
+
+You can copy from the image, with a custom shape,
+although pasting + floating is not supported. The canvas is a fixed size
+and loaded images are adjusted to fit. A stamp tool is also included
+which is pre-loaded with pictures of delicious pie.
+
+![Piecasso](screenshot-paint2.png)
+
+> If you think this example app is neat and want to learn more about
+PyQt in general, [take a look at my ebook & online course
+"Create Simple GUI Applications"](https://martinfitzpatrick.name/create-simple-gui-applications)
+which covers everything you need to know to start building your own applications with PyQt.
+
+## Code notes
+
+### Event handling
+
+All tools are implemented with nested event handlers, which forward
+on events as appropriate. This allows for a lot of code re-used between
+tools which have common behaviours (e.g. shape drawing). Adding the select
+region animation requires a timer (to update the crawling ants) which
+added some complexity.
+
+### Flood fill
+
+This was the trickiest part of this app from a performance point of view.
+Checking pixels directly is far too slow (full-canvas fill
+time of approx 10 seconds). Most code to achieve this in Python sensibly
+uses numpy, but I didn't want to introduce a dependency for this alone.
+
+By exporting the image as a bytestring, then down-sampling to a boolean 
+byte-per-pixel (for match/no-match) to simplify the comparison loop, I
+could get it up to a reasonable speed.
+
+The search-to-fill algorithm is still pretty dumb though.
+
+