Get rgba uint8[] from ARGB_8888 bitmap

Question

I have a bitmap and I am trying to get the the data to be an rgba byte array. I can do bmp.getPixels but this is not in rgba bytes. My end destination was to feed this to an HTML5 canvas which requires an 4 elements (r, g, b, a) per pixel. Is this possible?

This is the code I am using to get my bmp:

Bitmap bitmap = Bitmap.createBitmap(view.getWidth(), view.getHeight(), Config.ARGB_8888);
Canvas canvas = new Canvas(bitmap);
view.draw(canvas);
// can do bmp.getPixels here but it doesnt give RGBA :(

I tried this:

bmp.copyPixelsToBuffer(ByteBuffer.wrap(buffer));

but the contents of buffer is extremely weird, it doesnt look like rgba to me, it looks like this:

[ 54, 59, 64, -1, 54, 59, 64, -1,

Those -1s especially look weird.

score 2 · Answer 1 · answered Aug 09 '15 at 08:29

2

Each element of the pixel array is an int, containing argb values. You can get values like that:

int alpha = Color.alphpa(pixel);
int red = Color.red(pixel);
int green = Color.green(pixel);
int blue = Color.blue(pixel);

answered Aug 09 '15 at 08:29

Simon Marquis

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Thanks @Simon, so the way I tried with `copyPixelsToBuffer` is wrong? – Noitidart Aug 09 '15 at 08:35
`copyPixelsToBuffer` won't help you if you're just trying to get argb values from a bitmap – Simon Marquis Aug 09 '15 at 08:38

score 1 · Accepted Answer · edited May 23 '17 at 12:22

1

Question was already asked here, I believe it's a hint to yours.

how to get RGB values of bitmap in android

edited May 23 '17 at 12:22

Community

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answered Aug 09 '15 at 08:15

scarto

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Thanks @scarto I updated my answer above to show you what I tried, things look just a little weird but I think I might have the data right. – Noitidart Aug 09 '15 at 08:23
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http://stackoverflow.com/questions/5010545/access-to-raw-data-in-argb-8888-android-bitmap – scarto Aug 09 '15 at 08:48
Thanks scrato thats a very interesting topic! – Noitidart Aug 09 '15 at 08:50

score 0 · Answer 3 · answered Aug 09 '15 at 10:05

0

So the RGBA bitwise manipulation out of pixel worked.

But copyPixelsToBuffer also worked, the only issue was I had to change the alpha from -1 to 255 and it matched the RGBA bitwise manip method too.

Thanks all for the help!

answered Aug 09 '15 at 10:05

Noitidart

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Get rgba uint8[] from ARGB_8888 bitmap

3 Answers3