Resize a large bitmap file to scaled output file on Android
android, bitmap, image, resize
Solution
No. I'd love for someone to correct me, but I accepted the load/resize approach you tried as a compromise.
Here are the steps for anyone browsing:
- Calculate the maximum possible `inSampleSize` that still yields an image larger than your target.
- Load the image using `BitmapFactory.decodeFile(file, options)`, passing inSampleSize as an option.
- Resize to the desired dimensions using `Bitmap.createScaledBitmap()`.
Problem
I have a large bitmap (say 3888x2592) in a file. Now, I want to resize that bitmap to 800x533 and save it to another file. I normally would scale the bitmap by calling `Bitmap.createBitmap` method but it needs a source bitmap as the first argument, which I can't provide because loading the original image into a Bitmap object would of course exceed the memory (see here, for example). I also can't read the bitmap with, for example, `BitmapFactory.decodeFile(file, options)`, providing a `BitmapFactory.Options.inSampleSize`, because I want to resize it to an exact width and height. Using `inSampleSize` would resize the bitmap to 972x648 (if I use `inSampleSize=4`) or to 778x518 (if I use `inSampleSize=5`, which isn't even a power of 2). I would also like to avoid reading the image using inSampleSize with, for example, 972x648 in a first step and then resizing it to exactly 800x533 in a second step, because the quality would be poor compared to a direct resizing of the original image. To sum up my question: Is there a way to read a large image file with 10MP or more and save it to a new image file, resized to a specific new width and height, without getting an OutOfMemory exception? I also tried `BitmapFactory.decodeFile(file, options)` and setting the Options.outHeight and Options.outWidth values manually to 800 and 533, but it doesn't work that way.