jpeg - How do I preserve all the original image data in a JPG in Android? -

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i'm working client color style guides immutable, , part of app there feature jpgs provided sent server.

i'm converting images bytestream , uploading thusly, images arrive colors different original.

here's code byte stream creation...

bytearrayoutputstream stream = new bytearrayoutputstream(); bitmap b = bitmapfactory.decoderesource(getresources(), uploadimgid); b.compress(bitmap.compressformat.jpeg, 100, stream);             byte[] bitmapdata = stream.tobytearray();

i'm using 100% compression, so, i'm not sure why it's altering image in way.

would more reliable move jpgs device's file system , upload file? alternatively, more reliable use pngs instead of jpgs? (i'm guessing png treats color information differently jpg does).

tia

the executive summary seem taking bitmap , compressing using jpeg. jpeg lossy. if colours must kept right, need lossless codec, such png.

the long story follows:

jpeg lossy codec. compresses pictures loosing information in pictures humans not notice.

this can occur in 2 stages:

a common, although not mandatory step before jpeg compression chroma downsampling. name implies, involves loosing color information humans not sensitive to.

in addition, dct transformation, next , mandatory step in jpeg, works eliminating picture fine details humans wont notice. can, in pictures (such sharp edges) cause further color changes.

png on other hand lossless codec - works eliminating redundancy in information in image, never loosing information. comprised rle followed lempel ziv encoding, totally reversible.

in short, use png , save original colors beware pictures bigger uploading time longer , cellular data bill might bigger well.


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