Image Decolorizer is an Android app developed by appure, under the Multimedia category and Photography subcategory. It is a free app that allows you to colorize specific areas of a grayscale image by using your finger.

The app works by first converting the original image to black and white. Once the image is in grayscale, you can use your finger to color the desired areas. The thickness of the brush can be regulated by zooming in or out of the image, making it easier to color smaller or larger areas.

Overall, Image Decolorizer is a simple and easy-to-use app that can be helpful for those looking to highlight specific areas of a photo. However, it should be noted that the app doesn't have many advanced features and is best suited for basic image editing tasks.