topic JSL- get values of pixels in 0-255 in Discussions

JSL- get values of pixels in 0-255

LR237787 — Fri, 09 Jun 2023 18:04:55 GMT

Hi all, I am trying to get pixel values in 0-255 using Get Pixels().

{r, g, b} = img << Get Pixels("rgb");

This gives me normalized values (0-1). How can I get the pixel values in 0-255?

Thanks!

Re: JSL- get values of pixels in 0-255

jthi — Thu, 11 Nov 2021 15:26:18 GMT

Just guessing here, but maybe it would be enough to just multiply by 255?

This link could also give ideas (and has additional links) What do the numbers returned by << Get Pixels(); correspond to?

Re: JSL- get values of pixels in 0-255

ian_jmp — Thu, 11 Nov 2021 15:44:43 GMT

I think there's more than one way to do this. But here's a reference and a JMP implementation:

Names Default To Here( 1 );

Web("https://web.stanford.edu/class/cs101/image-6-grayscale.html", JMP Window);

img = Open( "$SAMPLE_IMAGES/tile.jpg", jpg );
win = New Window( "tile(40,40)", img );
{r, g, b} = img << Get Pixels( "rgb" );

// Average the rgb values of each pixel and scale from [0, 1] to [0, 255]
nr = NRow(r);
nc = NCol(r);
r2 = Shape(r, 1, nr*nc);
g2 = Shape(g, 1, nr*nc);
b2 = Shape(b, 1, nr*nc);
g2 = VMean(VConcat(r2, g2, b2));
g = Shape(g2, nr, nc);
g = Round(g*255, 0);
dt = AsTable(g);
dt << setName("Greyscale");