Scramble a bitmap image

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Scramble a bitmap image

Postby jtwoods4 » Sun May 09, 2010 7:26 am

I am new to android development. I have been asked to write an function to scramble a bitmap image. A user can then enter a password and the image will unscramble.

I have managed to write the following code that works but takes way to long to execute due to the setPixels call.

I was thinking of an alternate solution of just drawing the original unscrambled image and then making some sort of transparent overlay bitmap with some sort of distortion effect. When the user enters the correct password the overlay fades away.

Please help!

protected void onDraw(Canvas canvas)
//Some of the variables are global but I left out that code. This successfully runs.

int w = bitmap.getWidth();
int h = bitmap.getHeight();

Bitmap scrambled = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
int[]pixels = new int[w*h];

bitmap.getPixels(pixels, 0, w, 0, 0, w, h);

int color = 0;
Random random = new Random();

Paint paint = new Paint();

for (int i = 0; i < pixels.length; i++)
pixels[i] = pixels[random.nextInt(pixels.length - 1)];

scrambled.setPixels(pixels, 0, w, 0, 0, w, h);
canvas.drawBitmap(scrambled, 0, 0, paint);
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