创建位图与屏幕尺寸的保持比例

Question

I'm trying to make a Wallpaper Application. And I had big trouble during set wallpaper with bitmap. I have tried to figure out the answer for a week.

I want to set Bitmap in to wallpaper like

1. avoid crop
2. scaleType:fit_center(align center vertical, keep original bitmap's ratio)

How can I make it? Do I have to create new bitmap?

Answer 1

You need to resize the picture to make a new bitmap according to your screen size.

Here's the code:

        Bitmap bitmapOrg = BitmapFactory.decodeFile(getApplicationContext()
                .getFilesDir().toString() + "/images/" + imagename);

        Log.e("imageheight", "" + bitmapOrg.getHeight());
        Log.e("imagewidth", "" + bitmapOrg.getWidth());

        double imageheight = bitmapOrg.getHeight();
        double imagewidth = bitmapOrg.getWidth();

        DisplayMetrics metrics = getApplicationContext().getResources()
                .getDisplayMetrics();
        double screenwidth = metrics.widthPixels;
        double sreeenheight = metrics.heightPixels;

        Log.e("screennwidth", "" + screenwidth);

        double newratio = screenwidth / imagewidth;

        Log.e("newratio", "" + newratio);

        double newratio1 = newratio * imageheight;
        double newratio2 = newratio * (imagewidth - 10); // 10 margin in width

        Log.e("newratio1", "" + newratio1);

        int mainheight = (int) newratio1;
        // int mainweidth = (int) imagewidth;
        int mainweidth = (int) newratio2;
        Log.e("Mainheight", "" + mainheight);
        Log.e("Mainweidtht", "" + mainweidth);

        // Here you will get the scaled bitmap
        Bitmap new_ScaledBitmap = Bitmap.createScaledBitmap(bitmapOrg, mainweidth,mainheight, true);
       // Use this bitmap as wallpaper

Answer 2

To fit the Bitmap to the screen without cutting anything of, you first have to decide if the aspect ratio is bigger than the one the screen has or smaller. If the image aspect ratio is bigger than the screen aspect ratio, that means the bitmap is higer and/or not as wide as the screen, like the second image in the question. So you should scale the image based on the height like this:

if(imageWidth/imageHeight > screenWidth/screenHeight){
    scaleFactor = screenHeight/imageHeight;
    imageXPosition = screenWidth/2-imageWidth/2;
    imageYPosition = 0;

Else the image should be scaled based on the width like this:

}else{
    scaleFactor = screenWidth/imageHeight;
    imageXPosition = 0;
    imageYPosition = screenWidth/2-imageWidth/2;
}

You can use these values to draw the bitmap using a Matrix or create a scaled Bitmap with the dimensions imageWidth*scaleFactor and imageHeight*scaleFactor and draw it at imageXPosition | imageYPosition (this is more memory saving.