Reduce the size of a bitmap to a specified size in Android

问题

I want to reduce the size of a bitmap to 200kb exactly. I get an image from the sdcard, compress it and save it to the sdcard again with a different name into a different directory. Compression works fine (3 mb like image is compressed to around 100 kb). I wrote the following lines of codes for this:

String imagefile ="/sdcard/DCIM/100ANDRO/DSC_0530.jpg";
Bitmap bm = ShrinkBitmap(imagefile, 300, 300);

//this method compresses the image and saves into a location in sdcard
    Bitmap ShrinkBitmap(String file, int width, int height){

         BitmapFactory.Options bmpFactoryOptions = new BitmapFactory.Options();
            bmpFactoryOptions.inJustDecodeBounds = true;
            Bitmap bitmap = BitmapFactory.decodeFile(file, bmpFactoryOptions);

            int heightRatio = (int)Math.ceil(bmpFactoryOptions.outHeight/(float)height);
            int widthRatio = (int)Math.ceil(bmpFactoryOptions.outWidth/(float)width);

            if (heightRatio > 1 || widthRatio > 1)
            {
             if (heightRatio > widthRatio)
             {
              bmpFactoryOptions.inSampleSize = heightRatio;
             } else {
              bmpFactoryOptions.inSampleSize = widthRatio; 
             }
            }

            bmpFactoryOptions.inJustDecodeBounds = false;
            bitmap = BitmapFactory.decodeFile(file, bmpFactoryOptions);

            ByteArrayOutputStream stream = new ByteArrayOutputStream();   
            bitmap.compress(Bitmap.CompressFormat.JPEG, 100, stream);   
            byte[] imageInByte = stream.toByteArray(); 
            //this gives the size of the compressed image in kb
            long lengthbmp = imageInByte.length / 1024; 

            try {
                bitmap.compress(CompressFormat.JPEG, 100, new FileOutputStream("/sdcard/mediaAppPhotos/compressed_new.jpg"));
            } catch (FileNotFoundException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }


         return bitmap;
        }

回答1:

I found an answer that works perfectly for me:

/**
 * reduces the size of the image
 * @param image
 * @param maxSize
 * @return
 */
public Bitmap getResizedBitmap(Bitmap image, int maxSize) {
    int width = image.getWidth();
    int height = image.getHeight();

    float bitmapRatio = (float)width / (float) height;
    if (bitmapRatio > 1) {
        width = maxSize;
        height = (int) (width / bitmapRatio);
    } else {
        height = maxSize;
        width = (int) (height * bitmapRatio);
    }
    return Bitmap.createScaledBitmap(image, width, height, true);
}

calling the method:

Bitmap converetdImage = getResizedBitmap(photo, 500);

Where photo is your bitmap

回答2:

Here is the solution that limits image quality without changing width and height. The main idea of this approach is to compress bitmap inside the loop while output size is bigger than maxSizeBytesCount. Credits to this question for the answer. This code block shows only the logic of reducing image quality:

        ByteArrayOutputStream stream = new ByteArrayOutputStream();
        int currSize;
        int currQuality = 100;

        do {
            bitmap.compress(Bitmap.CompressFormat.JPEG, currQuality, stream);
            currSize = stream.toByteArray().length;
            // limit quality by 5 percent every time
            currQuality -= 5;

        } while (currSize >= maxSizeBytes);

Here is the full method:

public class ImageUtils {

    public byte[] compressBitmap(
            String file, 
            int width, 
            int height,
            int maxSizeBytes
    ) {
        BitmapFactory.Options bmpFactoryOptions = new BitmapFactory.Options();
        bmpFactoryOptions.inJustDecodeBounds = true;
        Bitmap bitmap;

        int heightRatio = (int)Math.ceil(bmpFactoryOptions.outHeight/(float)height);
        int widthRatio = (int)Math.ceil(bmpFactoryOptions.outWidth/(float)width);

        if (heightRatio > 1 || widthRatio > 1)
        {
            if (heightRatio > widthRatio)
            {
                bmpFactoryOptions.inSampleSize = heightRatio;
            } else {
                bmpFactoryOptions.inSampleSize = widthRatio;
            }
        }

        bmpFactoryOptions.inJustDecodeBounds = false;
        bitmap = BitmapFactory.decodeFile(file, bmpFactoryOptions);

        ByteArrayOutputStream stream = new ByteArrayOutputStream();
        int currSize;
        int currQuality = 100;

        do {
            bitmap.compress(Bitmap.CompressFormat.JPEG, currQuality, stream);
            currSize = stream.toByteArray().length;
            // limit quality by 5 percent every time
            currQuality -= 5;

        } while (currSize >= maxSizeBytes);

        return stream.toByteArray();
    }
}

来源：https://stackoverflow.com/questions/16954109/reduce-the-size-of-a-bitmap-to-a-specified-size-in-android