Fresco is an Android library (supports Android 2.3 and above) developed by Facebook and dedicated to image loading. It handles such image operations as downloading, caching, transforming and drawing. Fresco provides useful out of the box features like progressive JPEG streaming and offers a lot of customization.
When handling images on a mobile device, a lot of things can go wrong - from failed network connection up to getting OOM crashes. One may also need to customize an image's appearance for which the Android system provides very few out of the box solutions.
That's basically what Fresco does: loading (network layer), displaying (animated GIF's, circle transformations etc.), handling (memory/disk cache, managing the cache).
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