We have set 7 criteria for rating the current free picture editing apps in the android market. These 7 criteria are:
Effects, Customization, User-Interface, Option to Save/Share, Ad supported, Online/Offline and Ability to move to SD card.
1) Little Photo
(overall score = 90% | user rating = 4.5)
“It is a really decent photo editing app available in the android market. Though its user interface is not that smooth, this little app offers tons of photo editing filters to spice up your picture.
Effects: 5/5
This photo editing app offers several artistic effects, literally more than any other free plus offline photo editing app available in the market.
Customization: 4/5
Customization refers to the added tools and plugins that can be used to personalize the overall look and feel of the photo. Little photo offers some simple tools in this category, but it comes nothing close when compared to competitors like PicsArt and PicSay.
User-Interface: 4/5
The user interface of little photo app is quite simple and straight forward. There’s no option to select effects the very first time an image is loaded. Tapping on the touch screen brings the full list of effects and customization it offers.
Saving and sharing Options: 5/5
Users can easily share their masterpiece via Flickr, Picasa, Facebook and Gmail.
Ad-supported: Yes (3.5/5)
This app sponsors some of the mobile advertisements. Advertisements popups in free apps are a big turn off for many users like me(who love to see a clean UI). But these advertisements support the developers to keep up the good work.
Offline: Yes (5/5)
Using an offline application is advantageous to the users who want to save their data usage costs.
Movable to SD card: Yes (5/5)
Internal memory is precious. No one wants their smartphones to perform poor due to low internal memory space. So phones with small internal memory should try this free photo editing app for sure 
2) PicsArt photo studio (former - PicsIn Photo studio)
(overall score = 94.28% | user rating = 4.5)
PicsArt photo studio is a very powerful photo editing app developed for android powered devices. The quality and quantity of effects plus the customization this app offers are unparalleled to any other photo editing app in the market. The user interface is rich in functions, but it may require a powerful phone like GALAXY S2 and Samsung GALAXY Note to work like a charm. Android tablets users should definitely try out this wonderful photo editing app (bigger screen of tablets powered by strong processors adds a wow factor while using this app)
Effects: 5/5
There are plenty of effects ranging from lomo, sepia, pop colors… to even HDR. The effects offered by picsart photo studio can easily win the heart of any android user. The new version even features a photo correction option which can be used to fix blemishes, marks, change eye color, fix red eye, etc..
Customization: 5/5
The user enjoys the freedom to personalize the photos with so many awesome effects like collage, pen drawing, paint brush, beautiful borders, stickers, custom texts etc. This app is the best free app in the market when it comes to photo customization. But some of the customizations may need network access to work properly!
User-Interface: 5/5
The highly neat, flexible and easy to use interface of this app, makes it stand out of the crowd.
Saving and Sharing Options: 5/5
PicsArt Photo Studio allows saving the edited photos to the SD card as well as it provides the sharing options( share via Bluetooth, Facebook, Picasa, Flickr, etc.) to the user.
Ad-Supported: Yes (3.5/5)
Offline: Yes, but requires network access to load graphics like stickers and frames (4.5/5)
Movable to SD card: Yes (5/5)
This app can be moved to SD card after installation, but takes around 3 MB of storage space.
(overall score = 90% | user rating = 4.5)
PicSay is the best editing app for those looking for the funky image customization in form of banners, stickers and thought clouds..The user interface is very clean and smooth. Almost every android phone is capable of running this amazing app.
The true potential of this free photo editing app is realized when it is upgraded to the full version – PicSay Pro(which offers loads of effects and customization)
Effects: 3.5/5 This app offers pretty simple and elegant effects like distort, pixelate, tint, etc. But again, these effects are simply not enough for a photo editing app of it’s kind. It is better if one upgrades to the full version.
Customization: 3.5/5 PicSay offers a wide range of customization in the form of thought balloons, cool stickers(hairstyles, hats, eyewear, etc.) But the list of stickers is limited in the free version. Again, there is a reason to upgrade to the full version.
User-Interface: 4.5/5
The user-interface is pretty simple and cool, but it’s not that good as compared to that of PicsArt app. Although the app is much lighter to run flawlessly on any android phone.
Saving and sharing options: 5/5
This photo editing app also includes interactive options to save and share your creations instantly.
Ad-Supported: No (5/5)
This app is completely free from ads, adding to it’s clean user-interface.
Offline: Yes, but may require network access to load graphics and stickers(5/5)
Movable to SD card: Yes (5/5)
4) FX Camera
(overall score = 80% | user rating = 4.4)
“FX Camera is a fun photo editing app that primarily aims at replacing the stock camera of your android device with some pretty cool effects like fish eye, toy camera, lomo effects and so on ”
This app tops the cart of the android market with the highest number of user rating so far in the free category. 
Effects: 3/5
FX Camera comes preloaded with five basic effects under the name – toy camera, polandroid, fisheye, symmetric cam and Warhol.
Customization: 3/5 (Supports less flexibility to personalize)
User Interface: 4/5
Saving and Sharing options: Yes (5/5)
Ad-supported: No (3/5)
Offline: Yes (5/5)
Movable to SD card: Yes (5/5)
5) Photofunia
(overall score = 77% | User rating = 4.5)
Who is not aware of this most popular photo editing app ? With so many posters and frames to choose from, this app is a top choice for those who want to get their photos featured on magazine covers, attractive billboards, museums art-works, advertisements and much much more !!
Effects: 5/5
Customization: 1/5
User Interface: 4/5
Saving and Sharing options: 5/5
Ad-supported: Yes (3.5/5)
Offline: No. It obviously needs an active data or Wi-Fi connection (3.5/5)
Movable to SD card: Yes (5/5)
Please Read…
Disclaimer: The ratings given to above apps are purely subjective and these may vary from one person to another. This post is for educational purpose only and it has nothing to do with biased ratings or review. All these apps are fantastic and have unique features when contrasted to each other.
The users are requested to go through the photography section of the android market for better satisfaction and updated android market reviews..