How to Scale Bitmap to Screen Size

How to scale bitmap to screen size?

Try this to Decode the Bitmap :

Where imagefilepath is the path name of image,it will be in String covert that to File by using

File photos= new File(imageFilePath);

Where photo is the File name of the Image,Now you set your height and width according t your requirements.

public void main(){
    Bitmap bitmap = decodeFile(photo);
    bitmap = Bitmap.createScaledBitmap(bitmap,150, 150, true);
    imageView.setImageBitmap(bitmap);
} 

private Bitmap decodeFile(File f){
    try {
        //decode image size
        BitmapFactory.Options o = new BitmapFactory.Options();
        o.inJustDecodeBounds = true;
        BitmapFactory.decodeStream(new FileInputStream(f),null,o);              
        //Find the correct scale value. It should be the power of 2.
        final int REQUIRED_SIZE=70;
        int width_tmp=o.outWidth, height_tmp=o.outHeight;
        int scale=1;
        while(true){
            if(width_tmp/2<REQUIRED_SIZE || height_tmp/2<REQUIRED_SIZE)
                break;
            width_tmp/=2;
            height_tmp/=2;
            scale++;
        }

        //decode with inSampleSize
        BitmapFactory.Options o2 = new BitmapFactory.Options();
        o2.inSampleSize=scale;
        return BitmapFactory.decodeStream(new FileInputStream(f), null, o2);
    } catch (FileNotFoundException e) {}
        return null;
}

How to get scaled bitmap with respect to screen size with out getting Out of memory exception

1. What is a good way of creating the bitmap with respect to screen with and height with minimum memory consumed ?

   1. Never ever create a Bitmap with the screen height or width, because that will be very huge based on the density of the device.Instead use the height and width of the screen and calculate the aspect ratio. Now fix the height to a constant value (like 1200px) and then calculate the width based on the aspect ratio. The ImageView or any other view will scale this properly.
   2. If you really want transparency then use Bitmap.Config.ARGB_8888, if not could use RGB_565 or something else from the list here: http://developer.android.com/reference/android/graphics/Bitmap.Config.html
   3. Follow below points if you are not creating a fresh bitmap but decoding the bitmap from some resource:
      
      
      1. You need to use BitmapFactory.Options.inSampleSize to reduce the sampling. So how to calculate the inSampleSize if you already know the height and width? Refer this here: http://developer.android.com/training/displaying-bitmaps/load-bitmap.html
      2. So you do all this, and still the inSampleSize is not high enough and you get the OutOfMemoryError ? Don't worry, if this is the case, you need to catch this OutOfMemoryError and in that increase your inSampleSize and do the bitmap decode again. Put this logic in a loop, so the crash never happens.
         
         

2. How can I destroy the bitmap after using it ?

   1. This is really simple. Make sure to call the Bitmap.recycle() method. And remove all reference to the bitmap. Once you do this, the resource will be released and GC will do the cleaning up.

UPDATE: When you create the a bitmap with screen_width and screen_height you would end up with a huge bitmap. Instead create a less resolution bitmap that fits the whole screen. You can see the following code on how this is done.

    float screenHeight = displaymetrics.heightPixels;
    float screenWidth = displaymetrics.widthPixels;

    float aspectRatio  = screenWidth/screenHeight;

    int modifiedScreenHeight = 1000;
    int modifiedScreenWidth = (int) (modifiedScreenHeight * aspectRatio);

    Bitmap mBitmap = Bitmap.createBitmap(modifiedScreenWidth, modifiedScreenHeight, Bitmap.Config.ARGB_8888);

Now you got the bitmap with the right aspect ratio. You could use this bitmap as it is in the ImageView to fill the whole screen. Make sure you put android:scaleType="fitXY" for the ImageView.

Android: How do I scale a bitmap to fit the screen size using canvas/draw bitmap?

Rect frameToDraw = new Rect(0, 0, width, height);
RectF whereToDraw = new RectF(0, 0, width, height);

Take a look at the above code. Your are not scaling the picture. You are simply taking a part of the picture (in this case the whole picture) and pasting it somewhere (in this case the size of the original picture).

The width and heigth of the frameToDraw rectangle should be the width and height of your picture.

Scale Bitmap maintaining aspect ratio and fitting both width and height

Based on Streets of Boston's answer, I made this method that scales and returns any Bitmap to a desired width and height, fitting both dimensions (no blank space!). It automatically adapts to more horizontal or more vertical images.

public Bitmap resizeBitmapFitXY(int width, int height, Bitmap bitmap){
    Bitmap background = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
    float originalWidth = bitmap.getWidth(), originalHeight = bitmap.getHeight();
    Canvas canvas = new Canvas(background);
    float scale, xTranslation = 0.0f, yTranslation = 0.0f;
    if (originalWidth > originalHeight) {
        scale = height/originalHeight;
        xTranslation = (width - originalWidth * scale)/2.0f;
    }
    else {
        scale = width / originalWidth;
        yTranslation = (height - originalHeight * scale)/2.0f;
    }
    Matrix transformation = new Matrix();
    transformation.postTranslate(xTranslation, yTranslation);
    transformation.preScale(scale, scale);
    Paint paint = new Paint();
    paint.setFilterBitmap(true);
    canvas.drawBitmap(bitmap, transformation, paint);
    return background;
}

Scaling bitmaps for each resolution

If you wanna scale bitmap for each phone resolution, you should know phone screen size, scale ratio.

This code will return width (w) & height (h) of screen.

DisplayMetrics dMetrics = new DisplayMetrics();
activity.getWindowManager().getDefaultDisplay().getMetrics(dMetrics);
float density = dMetrics.density;
int w = Math.round(dMetrics.widthPixels / density);
int h = Math.round(dMetrics.heightPixels / density);

activity is instance of Activity which would you like to get screen size.

You have to remember that: When your device is in landscape orientation, w > h. When it in portrait orientation w < h.

So from width & height you can detect your device is in what orientation.

Example:

From w & h of device and ratio (which you want to scale) you can calculate new bitmap size to scale it.

public Bitmap getResizedBitmap(Bitmap bm, int newHeight, int newWidth) {
    int width = bm.getWidth();
    int height = bm.getHeight();
    float scaleWidth = ((float) newWidth) / width;
    float scaleHeight = ((float) newHeight) / height;
    // CREATE A MATRIX FOR THE MANIPULATION
    Matrix matrix = new Matrix();
    // RESIZE THE BIT MAP
    matrix.postScale(scaleWidth, scaleHeight);

    // "RECREATE" THE NEW BITMAP
    Bitmap resizedBitmap = Bitmap.createBitmap(bm, 0, 0, width, height, matrix, false);
    return resizedBitmap;
}

Scaled Bitmap maintaining aspect ratio

What about this:

Bitmap background = Bitmap.createBitmap((int)width, (int)height, Config.ARGB_8888);

float originalWidth = originalImage.getWidth(); 
float originalHeight = originalImage.getHeight();

Canvas canvas = new Canvas(background);

float scale = width / originalWidth;

float xTranslation = 0.0f;
float yTranslation = (height - originalHeight * scale) / 2.0f;

Matrix transformation = new Matrix();
transformation.postTranslate(xTranslation, yTranslation);
transformation.preScale(scale, scale);

Paint paint = new Paint();
paint.setFilterBitmap(true);

canvas.drawBitmap(originalImage, transformation, paint);

return background;

I added a paint to filter the scaled bitmap.

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