Scaled Bitmap maintaining aspect ratio
android, bitmap, scaling
Solution
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.
Problem
I would like to scale a `Bitmap` to a runtime dependant width and height, where the aspect ratio is maintained and the `Bitmap` fills the entire width and centers the image vertically, either cropping the excess or filling in the gap with 0 alpha pixels. I'm currently redrawing the bitmap myself by creating a `Bitmap` of all 0 alpha pixels and drawing the image `Bitmap` on top of it, scaling to the exact specified width and maintaining the aspect ratio, however, it ends up losing/screwing up the pixel data. Here is how I'm doing it: ``` Bitmap background = Bitmap.createBitmap((int)width, (int)height, Config.ARGB_8888); float originalWidth = originalImage.getWidth(), originalHeight = originalImage.getHeight(); Canvas canvas = new Canvas(background); float scale = width/originalWidth; float xTranslation = 0.0f, yTranslation = (height - originalHeight * scale)/2.0f; Matrix transformation = new Matrix(); transformation.postTranslate(xTranslation, yTranslation); transformation.preScale(scale, scale); canvas.drawBitmap(originalImage, transformation, null); return background; ``` Is there a library out there or some better code that can do this better? I would like the image to look as crisp as possible, but I knew that my function wouldn't provide a great result. I know I could have the image stay fine by using integer scaling, instead of float scaling, but I need the width to be 100% filled. Also, I know about an `ImageView`'s `Gravity.CENTER_CROP` capability, however, that also uses integer scaling, so it cuts off the width of the image when it shouldn't.