How to change the size of the image without changing resoultion?

Question

I am developing an app in which i want to reduce the size of my image.For example if size is 1MB then i want it to get reduce into kb.

But resolution should not get changed.

Can anyone help in this?

I tried this code but its not working

 public static Bitmap resizeBitMapImage1(String filePath, int targetWidth, int targetHeight) {
 Bitmap bitMapImage = null;
 try {
     Options options = new Options();
     options.inJustDecodeBounds = true;
     BitmapFactory.decodeFile(filePath, options);
     double sampleSize = 0;
     Boolean scaleByHeight = Math.abs(options.outHeight - targetHeight) >= Math.abs(options.outWidth
             - targetWidth);
     if (options.outHeight * options.outWidth * 2 >= 1638) {
         sampleSize = scaleByHeight ? options.outHeight / targetHeight : options.outWidth / targetWidth;
         sampleSize = (int) Math.pow(2d, Math.floor(Math.log(sampleSize) / Math.log(2d)));
     }
     options.inJustDecodeBounds = false;
     options.inTempStorage = new byte[128];
     while (true) {
         try {
             options.inSampleSize = (int) sampleSize;
             bitMapImage = BitmapFactory.decodeFile(filePath, options);
             break;
         } catch (Exception ex) {
             try {
                 sampleSize = sampleSize * 2;
             } catch (Exception ex1) {

             }
         }
     }
 } catch (Exception ex) {

 }
 return bitMapImage;

}

Using this code it reduces the resolution but not much size of the image.

I also tried

public static Bitmap reduceImgSizeToHundredKB(Bitmap bitmap) {
Bitmap scaled = bitmap;
try {
 ByteArrayOutputStream stream = new ByteArrayOutputStream();
  bitmap.compress(Bitmap.CompressFormat.JPEG, 70, stream);

 } catch (Exception e) {
 // TODO Auto-generated catch block
 e.printStackTrace();
  return null;
 }
   return scaled;

}

Answer 1

If you don't want to resize your image then your only option is to compress it.

Here is an example on how to do that:

byte[] data = null;
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    bi.compress(Bitmap.CompressFormat.JPEG, 100, baos);
    data = baos.toByteArray();

Answer 2

In my thought, In most cases, we can't do that. Because it related to resolution of the image and the color range of the image.

so, If we have a large image with a lot of colors, then reduce the size of the image will induce to reduce resolution of it.

Answer 3

There are two aproches: lossy (where you'll lose quality of the image) and lossless .

The answer provided by rickman is lossy so it will work well but reduce the quality of the image - it works particularly well for pictures taken with a camera.

The lossless approach is using PNG, which consists of using Bitmap.CompressFormat.PNG as argument to the compress method.

A not as well known but very efficient format is WebP . It's also available as an argument to the compress method ( Bitmap.CompressFormat.PNG ). I'd suggest testing with WebP, specially considering it supports both lossy and lossless compression.

Answer 4

Use this method if you are decoding from path

 public Bitmap decodeSampledBitmapFromPath(String path, int reqWidth,
    int reqHeight) {

final BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeFile(path, options);

options.inSampleSize = calculateInSampleSize(options, reqWidth,
        reqHeight);

// Decode bitmap with inSampleSize set
options.inJustDecodeBounds = false;
Bitmap bmp = BitmapFactory.decodeFile(path, options);
return bmp;
}
}
  public int calculateInSampleSize(BitmapFactory.Options options,
    int reqWidth, int reqHeight) {

final int height = options.outHeight;
final int width = options.outWidth;
int inSampleSize = 1;

if (height > reqHeight || width > reqWidth) {
    if (width > height) {
        inSampleSize = Math.round((float) height / (float) reqHeight);
    } else {
        inSampleSize = Math.round((float) width / (float) reqWidth);
     }
 }
 return inSampleSize;
}

Use this if you are decoding from resources

    public static Bitmap decodeSampledBitmapFromResource(Resources res, int resId,
    int reqWidth, int reqHeight) {

    // First decode with inJustDecodeBounds=true to check dimensions
    final BitmapFactory.Options options = new BitmapFactory.Options();
    options.inJustDecodeBounds = true;
    BitmapFactory.decodeResource(res, resId, options);

    // Calculate inSampleSize
    options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight);

     // Decode bitmap with inSampleSize set
     options.inJustDecodeBounds = false;
     return BitmapFactory.decodeResource(res, resId, options);
    }

public static int calculateInSampleSize(
    BitmapFactory.Options options, int reqWidth, int reqHeight) {
 // Raw height and width of image
 final int height = options.outHeight;
  final int width = options.outWidth;
int inSampleSize = 1;

if (height > reqHeight || width > reqWidth) {

// Calculate ratios of height and width to requested height and width
final int heightRatio = Math.round((float) height / (float) reqHeight);
    final int widthRatio = Math.round((float) width / (float) reqWidth);

// Choose the smallest ratio as inSampleSize value, this will guarantee
// a final image with both dimensions larger than or equal to the
// requested height and width.
inSampleSize = heightRatio < widthRatio ? heightRatio : widthRatio;
 }

 return inSampleSize;
}

Answer 5

If you want to reduce the file size of the image without losing a great ammount of quality you can do this: First you need to flatten the image, then save it for web (ctrl+alt+shift+s) Then select the preset PNG-8 128 Dithered. You can now customize this preset by setting the colors to "256", then select "selective" under the PNG-8, under "selective" change dither to "diffusion", deselect the "interlaced" option and make shure that the web snap option is set to 0%.