Question

I would like to get a bitmap’s dimensions in Android without reading the entire file.

I tried using the recommended inJustDecodeBounds and a custom InputStream that logged the read()s. Unfortunately based on this, the Android BitmapFactory appears to read a large amount of bytes.

Similar to:
Java/ImageIO getting image dimensions without reading the entire file? for Android, without using ImageIO.

Answer 1

You are right to use inJustDecodeBounds. Set it to true and make sure to include Options in decode. This just reads the image size.

There is no need to read a stream. Just specify the path in the decode.

BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeFile(<pathName>, options);
int imageHeight = options.outHeight;
int imageWidth = options.outWidth;