I am currently working on a small project, which shall load an image from an URL, resize and change it's colour depth to only 16 colours using a specified colour palette. The main problem for me is, that I want a program, which I can use on an Android device and on a desktop computer.
Do you know a good image processing library which works on both systems?
Thanks in advance.
There are several tools:
ImageJ, http://rsbweb.nih.gov/ij/
Fiji, http://fiji.sc/wiki/index.php/Fiji
IMMI, http://www.burgsys.com/image-processing-software-free.php
BoofCV: http://boofcv.org
The answers on this page are quite dated as of February 2014. I was searching to find a free Android image processing library and I came across the Stanford lecture notes here: http://www.stanford.edu/class/ee368/Android/index.html
Investigating a bit further, I found out that they are using OpenCV in their course material. It has a Java interface (along with many other languages), but the library is written natively in C++. They state that:
Along with well-established companies like Google, Yahoo, Microsoft,
Intel, IBM, Sony, Honda, Toyota that employ the library, there are
many startups such as Applied Minds, VideoSurf, and Zeitera, that make
extensive use of OpenCV.
I am excited(!) to have found this, looking forward to going home and giving it a go.
The Android NDK allows you to use an existing C/C++ library that does not require java.awt or any of the Android classes. For example, you could easily compile libpng as a shared library for Android and then write a JNI interface to pass images from the Java layer to the png library. Similarly, you will also be able to compile libpng as a shared library for your desktop computer and use it from there.
I recently wrote a tutorial on how to compile open-source libraries for Android. If you browse the Android source, you will find some classes that use the skia graphics library via jni. I have not used skia before, but since Android has skia in its base framework, it should not be too difficult to get it to work in your app/desktop program.
Writing cross-platform programs has been an area of active interest amongst the mobile developers community, and some engines such as libgdx have gotten really good at it. So what you are attempting is definitely possible.
Octoate,
I don't think there is a library that exists that does what you want, the reason for that is on non-mobile platform every graphical operation you are going to use in Java is going to use the Java2D rendering pipeline to some degree. On Android, this doesn't exist.
Android provides its own graphical pipeline for image manipulation and actually simplifies a lot of things that are more complicated in standard Java.
All that being said, it looks like you found a library (JJIL) that acts as an abstraction layer on top of these differences, in that case I would be a bit worried about performance and do some testing in your own code to see how it performs compared to the platform methods. For example, I saw this quote from JJIL:
allows images to be converted from Android bitmaps into JJIL RgbImages
When I look at the source for RgbImages, it looks like the image data gets converted and stored in an internal array; all of those layers of abstraction are going to cost you CPU time and memory, especially as images on mobile devices get bigger due to higher resolution cameras and high-bandwidth connections.
This may not be that big of an issue, but again, you'll probably want to do some profiling/testing/performance comparisons.
Any pure Java library should work on both platforms. A Google search of "Java image processing library" produced several results. Try to find the lightest weight lib that serves your purposes since memory and CPU are limited on mobile devices.
Barry
Related
To get a better understanding of what I'm actually asking let me outline my situation (I think the wording of my question is off, but couldn't think of how to word it better).
I'm currently working in a team of 4 people to develop a basic OCR app. I'm focused on the algorithm side, developing the pre-processing and implementing the OCR. I want as little to do with the app side as possible; as from what I've read so far, it is quite a steep hill to climb and I have enough to do without learning to develop the app from scratch.
So my questions are:
Is it possible to develop my code in a black-box style that I can hand to the app developer and say "Here's a list of functions, go for your life"
Is it possible to do the aforementioned in a way that I can test without the Android emulators?
Is it possible I can do all that without even needing the Android SDK? (given that I can develop my code to deal with specific formats of information. e.g. int[][] for pixel data)
You can certainly write and develop the algorithm without a dependency on the Android SDK, and ship an artifact (whether source code or a JAR) to the Android developers.
However, you will be able to reduce the length of the feedback loop if you at least have an Android test project that takes whatever artifact you ship to the Android developers, and run at least some tests on it - given the number of differences between the Android and Java SE runtimes, it is practically guaranteed that you will run into bugs due to platform differences.
Update: If you write native code or use a native library, I do not think you could easily give a working artifact without using the Android NDK.
As long as your code has no reliance on the Android SDK then certainly you can develop and test without it. Just be certain your code also has no reliance on other APIs (AWT, for example) which are not on the Android platform if Android is your intended target. Finally, be sure that testing is complete within the Android environment, once you're satisfied things are working in general.
I am getting ready to start a little Android development and need to choose a language. I know Python but would have to learn Java. I'd like to know from those of you who are using Python on Android what the limitations are. Also, are there any benefits over Java?
Most of the points mentioned by Andrew stand, I just wanted to mention that python can be and is used for full fledged Apps published on GooglePlay and even iOS. I can't speak for other frameworks but here are some examples of Apps published using Kivy.
Process Craft Google Play iOS
Fantasy War hammer
PreseMT is a multitouch presentation maker
Memo robots
Ground Truth
Kaleidoscope
Showcase demo example from Kivy project
DefelectTouch game iOS
Bargenius and many more...
On Packaging we have tried to make it as simple as possible, we also provide
A pre-built VM that can be used to make your apk with you having to do nothing except
copying your project dir over and running one command.
On GUI, yes the ui is custom, by default(tries to match Android's Holo theme). However it can be customised to resemble other look and feels, although I haven't tried it personally.
Oh and as long as one is talking about python based apps on android, I found this project mentioned on stackoverflow PyMob, their apps page mentions some interesting apps .
I investigated this recently for similar reasons. My conclusions were that I could not use Python to develop a native-looking application, which is what I wanted at the time. Specifically:
Python can't receive callbacks from the Java UI classes, so you can't use any native Java UI elements such as ListView, etc. Only dialog boxes etc. are easily available. If you have a totally custom UI such as a game, you can try PyGame for Android, or you could look at Kivy, which also uses PyGame.
Packaging of Python applications is very difficult, especially because the Python interpreter is not included on Android by default. The Kivy and PyGame teams are making some intermittent progress on this.
Because of the aforementioned issues, Python is essentially never used to make full fledged applications published in the app store, and so the literature on how to handle the many sundry issues with SL4A (Scripting Layer For Android) is very thin.
So, if you want to make an application that uses native UI elements, that you can actually distribute in the Play Store, or both, Python is regrettably not an option.
I have developed Android Apps on the market, coded in Python. Downsides:
Thus far my users must download the interpreter as well, but they are immediately prompted to do so. (UPDATE: See comment below.)
The script does not exit properly, so I include a webView page that asks them to goto:Settings:Apps:ForceClose if this issue occurs.
Is there a LWJGL port for Android available? (does not matter if the phone needs to rooted)
Things have happened since this question was answered in 2011.
It is new that LWJGL has support for Android.
The linked repo has the setup instructions and the demo, the actual code is in the LWJGL3 repo under the Android branch.
I've been using it for a while now, and this library has a bunch of useful features that aren't just connected to OpenGLES, OpenAL, OpenVR and Vulkan, but it also has a lot of utilities for things like 3D model loading, layouts, dialogs, fonts and a lot more. Meaning the Android port of LWJGL is a considerable add-on to the current OpenGL ES support.
As for other libraries though, you can use no libraries because of the native support. Alternatively, you can use LibGDX or jMonkeyEngine, those are the only two others I know of and have used. Note that these are frameworks and not libraries like LWJGL, meaning they set up a given system you have to follow (one of the reasons I dislike them). It's harder implementing custom features without having to bring out a lot of other parts of the framework that aren't that well documented.
One of LWJGL's main features is its OpenGL support. Android natively supports OpenGL ES so there's basically no need for LWJGL. As for the rest of LWJGL, it doesn't apply on the Android platform anyway - for example there is obviously no mouse to an Android device - so I don't see a direct LWJGL port ever being developed.
Check out the Android reference, especially the android.opengl package, for a good starting point.
A good 3D and 2D engine that uses LWJGL and works well for Android development (and also Desktop and Web Apps) is libGDX.
I can't say for sure, but during last autumn I was searching for quite a long time for that and couldn't find anything. So I would say no, but don't bank on that.
I just ordered an Android smartphone and want to start playing around with creating my own applications. Now the question is which language to use, the native Java or Python using SL4A (former ASE).
I tend to Python, as I know it much better than Java, but I'm wondering what I would be missing using a "second class" language on Android. On the SL4A website it is also stated to be alpha quality software, which is not exactly encouraging.
I'm also not quite sure what the limitations of the scripting environment are and if they would be problematic.
At the moment you cannot create a releasable program with Python (or any other scripting language) using SL4A. I have heard rumours that this is something Google is working on, but even if they do enable it Python apps are likely to be slow and power-hungry compared to Java. Also the scripting API only gives you access to a limited subset of the native Java API. I would not consider using SL4A for serious development work at the moment, only for one-off scripts and prototyping.
Take a look at Scala. It is a statically typed language on the JVM, but uses type inference to remove most of the noise that you get in Java. It also fully supports functional programming, and has a lot of pythonish features. Because it is statically typed it is as efficient as straight Java with none of the disadvantages. IMHO it is the language that Java should have been in the first place.
A lot of people are blogging about using Scala on Android, so Google around for more information.
More likely will depend what type of applications you will develop.
I would start with Java to become familiar with Android SDK. Anyway first you need to look into some examples, tutorials. Most of them are done in Java, and only a few, probably on the dev site of SL4A for that.
Also there is native development Android NDK, that can be programmed with C++.
But anyway Java rules for general applications.
Adding an update to Dave Kirby's answer:
Issue 55, Distribute scripts as APKs, in the issue tracker at SL4A deals specifically with that.
There is a solution being worked out (may be complete by now) described at SharingScripts. The only issue seems to be that you need to have a interpreter APK already installed.
you may want to check out Ruboto it is a framework for developing Android apps based on JRuby which means your JRuby code can call Android APIs and can also be called back from the Android Java side.
Here is an introduction article .
Consider ising Kivy, if you want to write Android apps with Python. The process of packing script to .apk file is described here.
The problem is, resulting .apk will be big (~7Mb for 300Kb data). It is obvious, because you need to pack there Python runtime and all libraries.
Another solution I have heard of, is Pygame for Android, but it works on lower lewel, so you need to draw graphics manually.
Unfortunately, I have not tried any of this ways yet, but it looks, that I'm going to start using kivy soon.
I am in the concept phase of an application that is going to have a lot of Audio/Video input and output. I want to do it in Java; but somehow am not fully convinced yet. What do you think? How bad could it be? And any advices?
Why I am thinking Java:
It's the language I'm most comfortable with.
Easier cross platform migration would be a bonus.
Cannot afford commercial platforms (like .NET) or not good enough in other free alternatives (like Python)
I'm also slightly inclined towards C++/Qt; but that would take more time for me as I'm not great in that and I am a bit worried about maintainability.
If you're interested, check out Xuggler. It exposes all the power of FFmpeg, but as a Java API that runs on Windows, Mac and Linux. The advantage is you get all the power of FFmpeg but from Java. The disadvantage is it requires the FFmpeg native DLLs/shared-libraries to be installed.
Easier cross platform migration would be a bonus.
Audio and video means you will be dealing with dedicated native libraries and JNI-wrappers for each supported platform; in this case, the cross-platform argument for Java does not really apply.
I believe that when you want to write an audio/video application, the programming language you will use is the second most important thing. The most important thing is the audio/video framework your application will use since this is what defines your capabilities.
I am aware of two popular generic video frameworks that can be used to accesd most multimedia types: Directshow and ffmpeg. Directshow is tied with windows, so only ffmpeg is left.
Ffmpeg has versions in both windows and unix and, although it is written in C, it can be used from a lot of languages.
There is even a number of java wrappers for ffmpeg (for instance, take a look at xuggle)!
C++ would be the first choice because of performance concerns often present in Audio/Video processing as well as the range of available libraries for video/audio.
You do make a good point about being familiar with Java. If you are pressed for time, this is even more important. However if you can spare some time for learning, C++ would be well worth it.
Regarding .NET: The .NET SDK with everything you need is freely downloadable. Get hold of a free IDE such as SharpDevelop and you are up and running. It's Visual Studio that costs money, you don't need Visual Studio to do .NET development.
Rusty.in,
How about trying to do JavaFX Media API. Recently, the version of the JavaFX is 1.2.0 with GUI Application as well. It supports the Swing. The grammar is based on the script style; however, you can deploy the existing Swing components into the JavaFX.
I hope it helps.
Tiger
Rusty, what did you wind up doing? I too have a video app I'd like to do, but really would prefer Java/JavaFX over C++. The thing about the using Flash and/or the current JavaFX video support is that Flash video playback is not frame-accurate. I really need to be able to stop/start/step on individual frames like you can with QuickTime.
Has anyone tried doing playback with Xuggler and Java/JavaFX?