http://appinventor.mit.edu/extensions/
It is said to be "Unsupported" materials, but intelligible Java source code has been released. The main functions of this extension are as follows:
- Fetch two images into the application, then creates an image combining the two.
- Give a weight to decide which image to adopt strongly.
- For all the pixels, for each of the elements of R, G, B, A, both images are combined according to the weight. It is as follows: (pixel in image C) = weight * (pixcel in image A) + (1 - weight) * (pixcel in image B)
- Writes the image of the join result to external storage. In doing so, give write permission with annotation @UsesPermissions.
- Basic operation of pixels of an image
- How to make a function block with and without return value
- Generation of user event and its processing
- How to set properties (image size, weight, etc.)
After understanding this Java source program, I made a very simple application using this extension. The following figure shows the entire source program of this application. Of course, thanks to this Exrensions block, this is extremely consice. Furthermore, after preparing the Java source list, you do not need to set up the build environment yourself. The following cloud builder will take care of everything.
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| Complete source program using Extensions blocks |
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| Original images(above) and the combined image(blow) |
With this experience as a clue, you want to develop yet another unique Extensions. The following reference sites would help you.
# How to make Extension concretely
http://ai2.appinventor.mit.edu/reference/other/extensions.html
# Java source code for existing blocks in App Inventor
https://github.com/mit-cml/appinventor-sources/tree/master/appinventor/components/src/com/google/appinventor/components/runtime
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