How to keep image quality same in BitmapFactory

问题

I've converted an bitmap image into string to save it:

............
Bitmap photo = extras.getParcelable("data");
ByteArrayOutputStream baos = new ByteArrayOutputStream();
photo.compress(Bitmap.CompressFormat.JPEG, 100, baos);
byte[] b = baos.toByteArray();
String encodedImage = Base64.encodeToString(b, Base64.DEFAULT);

Then I retrieve the bitmap from string to set an activity's background just like that:

byte[] temp = Base64.decode(encodedImage, Base64.DEFAULT);
Options options = new BitmapFactory.Options();
options.inScaled = false;
Bitmap bitmap = BitmapFactory.decodeByteArray(temp, 0,
                temp.length, options);
Drawable d = new BitmapDrawable(getResources(), bitmap);
getWindow().setBackgroundDrawable(d);

Everything works fine but the image quality reduces tremendously. How can I keep the image quality same as the original image? Did I do something wrong here that have reduced the quality?

回答1:

You are having here a tradeoff situation between picture quality and memory usage. Take a look at this line:

photo.compress(Bitmap.CompressFormat.JPEG, 100, baos);

photo.compress is obviously decreasing your image resolution in a factor given by the second parameter, unfortunately, this is the best quality you can get, since between 0 - 100, 100 stands for the best quality you can get. Now, you have another option, depending on the original picture's size you can just save the image without compressing it, but be aware that most cases this doesn't work and Jalvik can throw an OutofMemoryException, hope this helps.

回答2:

JPEG is lossy, no matter what quality settings you use. If you want to keep the image unchanged, you have to use lossless compression. for example Bitmap.CompressFormat.PNG

来源：https://stackoverflow.com/questions/16745489/how-to-keep-image-quality-same-in-bitmapfactory

标签

android

bitmap

bitmapfactory