尝试使用java android canvas.drawImage镜像图片

Question

I'm having problems while trying to rotate a picture with java android canvas.drawImage. I'm doing a little game, and I'm painting different pictures on the screen using my drawImage function. However now I want to rotate some little images, I have created a function called drawMirroredImage for this. However now this little images don't appear on the same place.

Here is my code:

public void drawImage(Image Image, int x, int y) {
    canvas.drawBitmap(((AndroidImage) Image).bitmap, x, y, null);
}

public void drawMirroredImage(Image Image, int x, int y) {
    canvas.save();
    canvas.scale(-1.0f, 1.0f);
    canvas.drawBitmap(((AndroidImage) Image).bitmap, x - canvas.getWidth(), y, null);
    canvas.restore();   
}

Anyone knows what I'm doing wrong?

Lot of thanks for helping

Answer 1

Following will work for you. I found it somewhere on SO itself but don't remember where.

public static Bitmap getReflectionedBitmap(Context context,int resourceId,Bitmap originalImage,int reflectionGap) {

        if(originalImage==null)
        originalImage = BitmapFactory.decodeResource(context.getResources(),resourceId);

        int width = originalImage.getWidth();
        int height = originalImage.getHeight();

        // This will not scale but will flip on the Y axis
        Matrix matrix = new Matrix();
        matrix.preScale(1, -1);
        // Create a Bitmap with the flip matix applied to it.
        // We only want the bottom half of the image
        Bitmap reflectionImage = Bitmap.createBitmap(originalImage, 0,
                height / 2, width, height / 2, matrix, false);

        // Create a new bitmap with same width but taller to fit reflection

        Bitmap bitmapWithReflection = Bitmap.createBitmap(width,
                (height + height / 2), Config.ARGB_8888);
        // Create a new Canvas with the bitmap that's big enough for
        // the image plus gap plus reflection

        Canvas canvas = new Canvas(bitmapWithReflection);
        // Draw in the original image
        canvas.drawBitmap(originalImage, 0, 0, null);
        // Draw in the gap
        Paint deafaultPaint = new Paint();
        deafaultPaint.setColor(0xffffffff);
        canvas.drawRect(0, height, width, height + reflectionGap , deafaultPaint);

        canvas.drawBitmap(reflectionImage, 0, height + reflectionGap, null);

        Paint paint = new Paint();
        LinearGradient shader = new LinearGradient(0,
                originalImage.getHeight(), 0, bitmapWithReflection.getHeight()
                        + reflectionGap, 0x70ffffff, 0x00ffffff, TileMode.CLAMP);
        // Set the paint to use this shader (linear gradient)
        paint.setShader(shader);
        // Set the Transfer mode to be porter duff and destination in
        paint.setXfermode(new PorterDuffXfermode(Mode.DST_IN));
        canvas.drawRect(0, height, width, bitmapWithReflection.getHeight()
                + reflectionGap, paint);

        return bitmapWithReflection;
    }

I tweaked the snippet a little bit to use it with resource images as well.

Pass in null as parameter in place of Bitmap if you want to create reflection for images in resource.