Resizing a bitmap to a fixed value but without changing the aspect ratio

Question

I\'m looking for a solution for the following problem: how to change the size of a Bitmapto a fixed size (for example 512x128). The aspect ratio of the bitmap conte

Answer 1

I have stumbled upon the same problem a number of times in my projects and each time due to lack of time (and laziness) I would be satisfied with a less than optimum solution. But recently I found some time to crack down this particular issue. Here is my solution and I hope it helps someone down the line...

Bitmap scaleDownLargeImageWithAspectRatio(Bitmap image)
            {
                int imaheVerticalAspectRatio,imageHorizontalAspectRatio;
                float bestFitScalingFactor=0;
                float percesionValue=(float) 0.2;

                //getAspect Ratio of Image
                int imageHeight=(int) (Math.ceil((double) image.getHeight()/100)*100);
                int imageWidth=(int) (Math.ceil((double) image.getWidth()/100)*100);
                int GCD=BigInteger.valueOf(imageHeight).gcd(BigInteger.valueOf(imageWidth)).intValue();
                imaheVerticalAspectRatio=imageHeight/GCD;
                imageHorizontalAspectRatio=imageWidth/GCD;
                Log.i("scaleDownLargeImageWIthAspectRatio","Image Dimensions(W:H): "+imageWidth+":"+imageHeight);
                Log.i("scaleDownLargeImageWIthAspectRatio","Image AspectRatio(W:H): "+imageHorizontalAspectRatio+":"+imaheVerticalAspectRatio);

                //getContainer Dimensions
                int displayWidth = getWindowManager().getDefaultDisplay().getWidth();
                int displayHeight = getWindowManager().getDefaultDisplay().getHeight();
               //I wanted to show the image to fit the entire device, as a best case. So my ccontainer dimensions were displayWidth & displayHeight. For your case, you will need to fetch container dimensions at run time or you can pass static values to these two parameters 

                int leftMargin = 0;
                int rightMargin = 0;
                int topMargin = 0;
                int bottomMargin = 0;
                int containerWidth = displayWidth - (leftMargin + rightMargin);
                int containerHeight = displayHeight - (topMargin + bottomMargin);
                Log.i("scaleDownLargeImageWIthAspectRatio","Container dimensions(W:H): "+containerWidth+":"+containerHeight);

                //iterate to get bestFitScaleFactor per constraints
                while((imageHorizontalAspectRatio*bestFitScalingFactor <= containerWidth) && 
                        (imaheVerticalAspectRatio*bestFitScalingFactor<= containerHeight))
                {
                    bestFitScalingFactor+=percesionValue;
                }

                //return bestFit bitmap
                int bestFitHeight=(int) (imaheVerticalAspectRatio*bestFitScalingFactor);
                int bestFitWidth=(int) (imageHorizontalAspectRatio*bestFitScalingFactor);
                Log.i("scaleDownLargeImageWIthAspectRatio","bestFitScalingFactor: "+bestFitScalingFactor);
                Log.i("scaleDownLargeImageWIthAspectRatio","bestFitOutPutDimesions(W:H): "+bestFitWidth+":"+bestFitHeight);
                image=Bitmap.createScaledBitmap(image, bestFitWidth,bestFitHeight, true);

                //Position the bitmap centre of the container
                int leftPadding=(containerWidth-image.getWidth())/2;
                int topPadding=(containerHeight-image.getHeight())/2;
                Bitmap backDrop=Bitmap.createBitmap(containerWidth, containerHeight, Bitmap.Config.RGB_565);
                Canvas can = new Canvas(backDrop);
                can.drawBitmap(image, leftPadding, topPadding, null);

                return backDrop;
            }