{"id":481,"date":"2013-03-24T18:48:48","date_gmt":"2013-03-24T17:48:48","guid":{"rendered":"http:\/\/blog.ansuz.nl\/?p=481"},"modified":"2013-03-24T18:48:48","modified_gmt":"2013-03-24T17:48:48","slug":"renderscript","status":"publish","type":"post","link":"http:\/\/blog.ansuz.nl\/index.php\/2013\/03\/24\/renderscript\/","title":{"rendered":"Renderscript"},"content":{"rendered":"

To do some faster image manipulation I’ve been looking at Renderscript<\/a>.<\/p>\n

Renderscript provides a platform-independent computation engine that operates at the native level. Use it to accelerate your apps that require extensive computational horsepower.<\/p><\/blockquote>\n

This made it a better candidate than using the NDK with JNI<\/a>.\u00a0It’s also easier to maintain as an Android developer.<\/p>\n

What I wanted to achieve is a fast way to apply Gaussian blur<\/a>. Googling around will provide you plenty ways to do this in Java. It let me to a blog post about using a Convolution matrix<\/a> combined with various kernels to achieve different effects. Unfortunately doing this on large images in Java is slow.<\/p>\n

The other option was to use JNI, but I don’t feel confident enough about writing C\/C++. There are, however, some libraries out there worth looking at. OpenCV<\/a> and Lightbox’\u00a0PhotoProcessing<\/a> for instance. But when you’re just trying to use one or two effects, this seems a bit overkill.<\/p>\n

Last but not least is Renderscript. This is a bit more accessible than the NDK and only results in a slight loss of performance compared to using the NDK. The only requirement is Android 3+<\/a> (API level 11 and above).
\nIf you’re looking to get started with Renderscript, Google has a good introduction<\/a> and more\u00a0in-depth\u00a0article about the design goals of Renderscript<\/a>. The Renderscript reference<\/a> comes in very handy when you are writing your own scripts.
\nAt first I was happy to find the\u00a0ScriptIntrinsicBlur<\/a> class, but unfortunately that one is only available from API level 17. Discarding that option, I decided to implement my own class to create a Gaussian blur effect. To start work on a fast algorithm for Gaussian blur, I had a look at how this is being done for games and came across a blog post about “Efficient Gaussian blur<\/a>“. I’ve made a first (yet to be further optimized) version and tried it out, you can find the script at Github<\/a>. This implementation already renders a Gaussian blur effect extremely fast. It looks great when using the emulator, but unfortunately when used on a phone it seems to produce some scanline<\/a>-like side-effect.<\/p>\n

The biggest downside of Renderscript is that it is only available on Android 3+. It does, however, look like Google is working on a compatibility library for\u00a0Android 2.2. When you clone “https:\/\/android.googlesource.com\/platform\/frameworks\/support<\/wbr><\/wbr><\/a>“, there seems to be a “renderscript\\v8” folder. I tried building it using the supplied Make file, but there were some errors.<\/p>\n

I hope the compatibility library for Renderscript arrives soon, so it can be used across a bigger range of devices.<\/p>\n","protected":false},"excerpt":{"rendered":"

To do some faster image manipulation I’ve been looking at Renderscript. Renderscript provides a platform-independent computation engine that operates at the native level. Use it to accelerate your apps that require extensive computational horsepower. This made it a better candidate … Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[112],"tags":[119],"class_list":["post-481","post","type-post","status-publish","format-standard","hentry","category-android","tag-renderscript"],"_links":{"self":[{"href":"http:\/\/blog.ansuz.nl\/index.php\/wp-json\/wp\/v2\/posts\/481","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/blog.ansuz.nl\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/blog.ansuz.nl\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/blog.ansuz.nl\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/blog.ansuz.nl\/index.php\/wp-json\/wp\/v2\/comments?post=481"}],"version-history":[{"count":7,"href":"http:\/\/blog.ansuz.nl\/index.php\/wp-json\/wp\/v2\/posts\/481\/revisions"}],"predecessor-version":[{"id":489,"href":"http:\/\/blog.ansuz.nl\/index.php\/wp-json\/wp\/v2\/posts\/481\/revisions\/489"}],"wp:attachment":[{"href":"http:\/\/blog.ansuz.nl\/index.php\/wp-json\/wp\/v2\/media?parent=481"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/blog.ansuz.nl\/index.php\/wp-json\/wp\/v2\/categories?post=481"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/blog.ansuz.nl\/index.php\/wp-json\/wp\/v2\/tags?post=481"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}