Covert color to rgb value in java

Question

I know a formula to convert a colour to its RGB. Eg.

Color c=new Color(100,100,100);
Int rgb1= c.getRed()*65536+c.getGreen()*256+c.getBlue();

This is how we get single RGB value.

Using java programming

int rgb2=c.getRGB();

when I compare this two rgb1 and rgb2, they show a different value. What's wrong in my first equation. Please kindly solve my problem. Thanks

As a side note, a left-shift `a << b` is mathematically equivalent to a multiplication `a * 2^b`. It would be more idiomatic to do those multiplications as left-shifts since you are working with packed bytes rather than an actual number. `(red << 16) | (green << 8) | blue` — Radiodef, Apr 15 '17 at 15:58

score 1 · Accepted Answer · answered Apr 15 '17 at 15:49

1

That because the first way ignores the Alpha value of the color.
You can see that c.getAlpha() returns 255 and you don't use this value, but c.getRGB(); does use it, so it returns FF646464 (in hex base), which is different from 646464.

answered Apr 15 '17 at 15:49

TDG

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Did not think of that. Can you please show me how to add alpha value. – NEKIBUR RAHMAN Apr 15 '17 at 15:51
Look here - http://stackoverflow.com/questions/2534116/how-to-convert-get-rgbx-y-integer-pixel-to-colorr-g-b-a-in-java – TDG Apr 15 '17 at 15:53
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Here's an example like the one in the OP which shows this is the case. http://ideone.com/dWwtk8 – Radiodef Apr 15 '17 at 15:54
@Radiodef thanks for you answer. But i know that one. I just need a correct version of my first equation – NEKIBUR RAHMAN Apr 15 '17 at 16:02
If you mean an expression which uses multiplication, you can find that according to my other comment. `(c.getAlpha() * 16777216) + ...` http://ideone.com/CdzusM – Radiodef Apr 15 '17 at 16:05
Yes @Radiodef. You are right. Thanks a lot. That is helpfull. – NEKIBUR RAHMAN Apr 15 '17 at 16:15

Covert color to rgb value in java

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