Forking Picasso

Recently I started using this nice library, Picasso, for my Android projects.
Basically it’s a library which allows you to load any type of images (local or remote, assets or resources) asynchronously into your ImageView. It will load them in background for you, this not blocking the UI. It has also an internal cache system and it also comes with some useful features like “fade” ( when an image is loaded into the view it will automatically create a fade in effect ), “transform” ( you want to post transform the loaded bitmap ), “resize”, “fit” and more.

You can find a better explanation of the project here: http://square.github.io/picasso/

By the way, long story short, as often happens, when you start to use a 3rd party library you also find it’s limitations and you want to make your own changes to fit your particular needs. In fact I made a fork of this library starting adding my changes.

Here’s a first list of changes I made:

Cache

Added the possibility to use an external cache instance per request.
Example:

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// creating a cache object with 1MB max size
Cache cache = new LruCache( 1024*1024*1 );

// now create a new request which will use this cache object
Picasso.with( this ).load( file ).withCache( myCache ).into( imageView );

Remember to clear the cache when you don’t need that anymore ( using cache.clear() )

Generators

Generators can be used to load images which cannot be loaded using the common scheme convention. There are different situations when you need to generate a Bitmap which is not directly related to a file or url or even a real bitmap resource.

In this case you can use the scheme “custom.resource” with a Generator.
A Generator is a simple interface with only one method:

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public interface Generator {
   Bitmap decode( String path ) throws IOException;
}

So you can use a generator in this way:

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Picasso.with(this)
   .load( Uri.parse( "custom.resource://" + file ) )
   .withGenerator( new Generator() {
      @Override
         public Bitmap decode( String path ) throws IOException {
            return whatever(path);
         }
      } ).into( imageView );

Resize

Both the original Picasso methods resize and resizeDimen have been modified in the followings new methods:

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public RequestCreator resizeDimen(int targetWidthResId, int targetHeightResId, boolean onlyIfBigger);
public RequestCreator resize(int targetWidth, int targetHeight, boolean onlyIfBigger);

basically you can pass an option to skip the resize operation if the loaded bitmap is smaller than the passed `targetWidth` and `targetHeight`

BitmapFactory.Options

Picasso uses a default BitmapFactory.Options object, every time, to decode the required Bitmap.

I’ve added a method `withOptions` in the RequestCreator which allow you to pass your own Options object which will be used to decode the image.
Example:

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BitmapFactory.Options options = new BitmapFactory.Options();
options.inPreferredConfig = Config.RGB_565;

Picasso.with(this)
   .load(file)
   .withOptions(options)
   .into(imageView);

https://github.com/sephiroth74/picasso

  • Wesley Leung Kwan Lok

    I really like the idea of Generator that allows me to provide my custom bitmap decode method.
    Good work!
    btw, any chance of making a pull request and have these nice features merged to master branch? :)

    • http://www.sephiroth.it Alessandro Crugnola

      Thank you. I already did a pull request, but because of the many changes ( not only generators, I made other changes ) it was declined. That’s why I also published the fork on maven central.