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I know this question is already mentioned on some places (like here), but is there an easy way to read WebP images, like using a jar file?

It would be great to minimize the size of images of apps even on older devices.

Is it possible to read a WebP inputStream to a normal bitmap instance like you do with other formats, even on older android versions (older than ICS)?

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android developer
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2 Answers2

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The example you hae provided is quite good, to summarise it you need to follow such steps:

  • download the webp library, current version here
  • create in your Android "jni" folder, copy libwep content to it

  • in jni/Android.mk add:

    swig/libwebp_java_wrap.c \

    to LOCAL_SRC_FILES := \ and removeinclude $(BUILD_STATIC_LIBRARY), put instead include $(BUILD_SHARED_LIBRARY)

  • go to your project directory and run

    ./path-to-android-ndk/ndk-build

  • if you don't know how to use ndk, try here

  • if you compile successfuly, you obtain libwebp.jar, include it in your project build path

  • in you activity, you put firstly:

    static { System.loadLibrary("webp"); }

  • then you can read .webp file by InputStream (i.e. from assets folder):

    InputStream is = getAssets().open("image.webp");

  • download apache library from here, include it in your project build path

  • then you can read InputStream to byte array:

    byte[] encoded = IOUtils.toByteArray(is);

  • decode the file by libwebp:

    int[] width = new int[] { 0 };

    int[] height = new int[] { 0 };

    byte[] decoded = libwebp.WebPDecodeARGB(encoded, encoded.length, width, height);

  • convert to bitmap:

    int[] pixels = new int[decoded.length / 4];

    ByteBuffer.wrap(decoded).asIntBuffer().get(pixels);

    Bitmap bitamp = Bitmap.createBitmap(pixels, width[0], height[0], Bitmap.Config.ARGB_8888);

  • last lines taken form here

  • do with your bitmap whatever you want.

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Krzysztof Kacprzak
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  • looks cool. can't wait to check it out. can i also put the webP image files into the res/drawable folders instead of the assets folder? – android developer Jun 10 '13 at 09:36
  • yes, you can, like this: Drawable drawable = getResources().getDrawable(R.drawable.image); BitmapDrawable bD = (BitmapDrawable) drawable; Bitmap bitmap = bD.getBitmap();, byte[] encoded = stream.toByteArray(); an so on... – Krzysztof Kacprzak Jun 10 '13 at 18:55
  • oops didn't think about it enough. sorry. anyway, i'm not sure how other images are treated, but here it requires that the whole file will be loaded into byte array for the decoding. is this correct? is it the same on the other file formats? – android developer Jun 10 '13 at 21:27
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If your webp image is stored in assets folder then use this code to Read and show in imageView

try {
            InputStream inputStream = context.getAssets().open("yourfilename.webp");
            BufferedInputStream bufferedInputStream = new BufferedInputStream(inputStream);
            Bitmap bmp = BitmapFactory.decodeStream(bufferedInputStream);
            imageView.setImageBitmap(bmp);
           
        } catch (IOException e) {
            e.printStackTrace();
        }
Golu
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