How to resize a bitmap eficiently and with out los

问题:

I have a Bitmap with a size of 320x480 and I need to stretch it on different device screens, I tried using this:

Rect dstRect = new Rect();
canvas.getClipBounds(dstRect);
canvas.drawBitmap(frameBuffer, null, dstRect, null);

it works, the image fills the whole screen like I wanted but the image is pixelated and it looks bad. Then I tried :

float scaleWidth = (float) newWidth / width;
float scaleHeight = (float) newHeight / height;
Matrix matrix = new Matrix();
matrix.postScale(scaleWidth, scaleHeight);
Bitmap resizedBitmap = Bitmap.createBitmap(frameBuffer, 0, 0,
                width, height, matrix, true);
canvas.drawBitmap(resizedBitmap, 0, 0, null);

this time it looks perfect, nice and smooth, but this code has to be in my main game loop and creating Bitmaps every iteration makes it very slow. How can I resize my image so it doesn't get pixelated and gets done fast?

FOUND THE SOLUTION:

Paint paint = new Paint();
paint.setFilterBitmap();
canvas.drawBitmap(bitmap, matrix, paint);

回答1:

Resizing a Bitmap:

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;
}

Pretty self explanatory: simply input the original Bitmap object and the desired dimensions of the Bitmap, and this method will return to you the newly resized Bitmap! May be, it is useful for you.

回答2:

I am using the above solution to resize the bitmap. But it results portion of the image is lost.

Here is is my code.

 BitmapFactory.Options bmFactoryOptions = new BitmapFactory.Options();
            bmFactoryOptions.inPreferredConfig = Bitmap.Config.ARGB_8888;
            bmFactoryOptions.inMutable = true;
            bmFactoryOptions.inSampleSize = 2;
            Bitmap originalCameraBitmap = BitmapFactory.decodeByteArray(pData, 0, pData.length, bmFactoryOptions);
            rotatedBitmap = getResizedBitmap(originalCameraBitmap, cameraPreviewLayout.getHeight(), cameraPreviewLayout.getWidth() - preSizePriviewHight(), (int) rotationDegrees);

 public Bitmap getResizedBitmap(Bitmap bm, int newWidth, int newHeight, int angle) {
        int width = bm.getWidth();
        int height = bm.getHeight();
        float scaleWidth = ((float) newWidth) / width;
        float scaleHeight = ((float) newHeight) / height;
        Matrix matrix = new Matrix();
        matrix.postRotate(angle);
        matrix.postScale(scaleWidth, scaleHeight);
        Bitmap resizedBitmap = Bitmap.createBitmap(bm, 0, 0, width, height, matrix, true);
        DeliverItApplication.getInstance().setImageCaptured(true);
        return resizedBitmap;
    }

And here is the image height and width : Preview surface size:352:288 Before resized bitmap width : 320 Height : 240 CameraPreviewLayout width : 1080 Height : 1362 Resized bitmap width : 1022 Height : 1307