Format of TYPE_INT_RGB and TYPE_INT_ARGB

问题:

Could anyone explain for me how java stores color in TYPE_INT_RGB and TYPE_INT_ARGB ?
Do these lines of code work properly for calculating red, green and blue ?

int red= (RGB>>16)&255;
int green= (RGB>>8)&255;
int blue= (RGB)&255;

And what about TYPE_INT_ARGB ? How can I get red, green and blue from TYPE_INT_ARGB?

回答1:

The TYPE_INT_ARGB represents Color as an int (4 bytes) with alpha channel in bits 24-31, red channels in 16-23, green in 8-15 and blue in 0-7.

The TYPE_INT_RGB represents Color as an int (4 bytes) int the same way of TYPE_INT_ARGB, but the alpha channel is ignored (or the bits 24-31 are 0).

Look the javadoc of java.awt.Color and java.awt.image.BufferedImage.

回答2:

You are correct for TYPE_INT_RGB. The equivalent TYPE_INT_ARGB code would be:

int rgb = rgbColor.getRGB(); //always returns TYPE_INT_ARGB
int alpha = (rgb >> 24) & 0xFF;
int red =   (rgb >> 16) & 0xFF;
int green = (rgb >>  8) & 0xFF;
int blue =  (rgb      ) & 0xFF;

Spelling out the color elements for the bytes from most significant to least significant, you get ARGB, hence the name.

回答3:

These are constant values that indicate the color model of an instance of BufferedImage. These values do not themselves store the color.