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POViewing a small region of a Large Image in Android
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copied!<p>In a gist this is what I want to do:</p> <p><strong><em>I want to load a 100x100 region (any part) of a 5mega pixel Image into a Android Bitmap class so that I can draw it onto a canvas element</em></strong> Its that simple. Thats all I want to do. Thats it. Nothing more. Nothing less. Sounds simple enough. So before you have a smirk on your face, read on further down.</p> <p>I understand that this question has been asked a million times already. And I have also done my homework, researching it. Unfortunately I have hit a dead end from all sides. Maybe I need to make my question clear enough.</p> <p>There is a limit on the amount of heap the Android VM lets you allocate. So loading a large bitmap, even the one from its own camera (I own a Nexus S) is not possible by using the following function.</p> <pre><code>BitmapFactory.decodeStream(InputStream is) </code></pre> <p>Yes I could scale it by using <strong>BitmapFactory.Options</strong>, but how then should I zoom in?</p> <p>Now I am trying to design an image viewer which can smoothly zoom in/out from the image. Obviously that's not possible if I can't even load the image.</p> <p>In gingerbread we have a new class <strong>BitmapRegionDecoder</strong> , but I am designing my app for Froyo. All these classes have hooks into the native api which use the <strong>Skia 2D Graphics Library</strong>. The Android NDK does not give access to these api's also. Maybe there is a way to manually build Skia and use it to load a java bitmap. But I am not sure how?</p> <p>It seems to have been solved already (<a href="http://blog.javia.org/how-to-work-around-androids-24-mb-memory-limit/" rel="nofollow">http://blog.javia.org/how-to-work-around-androids-24-mb-memory-limit/</a>) in this app - <a href="https://market.android.com/details?id=image.viewer" rel="nofollow">https://market.android.com/details?id=image.viewer</a> by using the memory allocated in the native C code using <strong>malloc/new</strong>. But I cant figure out how?</p> <p>So make things clearer what I want is something that can zoom in/out of an image to full resolution. If possible it should be smooth or atleast it can be done in a separate thread.</p> <p>If I need to use OpenGL, then please give me a sample code also.</p>

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