Saving a Bitmap in Android

Question

I am trying to implement a Steganography project for Android. I have manipulated the pixel values and created a new bitmap. Now when i store the bitmap into the phone memory or memory card using

//fo denotes File output Stream
Bitmap.compress(Bitmap.CompressFormat.JPEG,100,fo);
//OR
Bitmap.compress(Bitmap.CompressFormat.PNG,100,fo);

and try accessing the pixels back using getPixels();

the values are reverted back to the original bitmap i.e. rather than the manipulated bitmap. Can anybody figure why this is?

score 1 · Answer 1 · answered Jan 26 '13 at 04:56

1

JPEG is lossy, it can change pixel values when compressing. Use PNG if you want to preserve colors.

answered Jan 26 '13 at 04:56

yoah

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score 1 · Answer 2 · edited May 23 '17 at 11:45

1

File myDir=new File("/sdcard/saved_images");
myDir.mkdirs();
Random generator = new Random();
int n = 10000;
n = generator.nextInt(n);
String fname = "Image-"+ n +".jpg";
File file = new File (myDir, fname);
if (file.exists ()) file.delete (); 
try {
       FileOutputStream out = new FileOutputStream(file);
       finalBitmap.compress(Bitmap.CompressFormat.JPEG, 90, out);
       out.flush();
       out.close();

} catch (Exception e) {
       e.printStackTrace();
}

look at this answer https://stackoverflow.com/a/7887114/964741

edited May 23 '17 at 11:45

Community

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answered Nov 27 '11 at 05:27

RajaReddy PolamReddy

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There is no problem in actually creating the file, but the pixel values of the bitmap changes.Is there a way to prevent it? – Desert Ice Nov 27 '11 at 08:41
For example the bitmap values for red , blue and green were 8,8,15 but after saving the bitmap the values were 16 16 16.Can anybody tell me how i can prevent this? – Desert Ice Nov 27 '11 at 14:08

Saving a Bitmap in Android

2 Answers2