using greythresh and im2bw

Figure 1 is great but BW is all black. Thoughts? Thanks

figure (1) 
scaled = 255 *  width/MAX; 
   imshow(uint8(scaled));
   level = graythresh(scaled)
  BW = im2bw(scaled,level);
  figure(2);
  imshow(uint8(BW))

Answer 1

[Walter Roberson]

BW is logical, just 0 and 1. When you uint8() that, you are creating an image with just uint8(0) and uint8(1), which is too dark to be visible.

You are also doing the grayscale conversion on a double array that is out of range for valid double coefficients, and that is affecting your output.

figure (1) 
scaled = 255 *  width/MAX;
scaled8 = uint8(scaled);
imshow(scaled8);
level = graythresh(scaled8);
BW = im2bw(scaled8, level);
figure(2);
imshow(BW)

[Douglas Brenner]

Figure 1 is now all white but figure 2 is right. However, this works.

   figure (1)
   scaled = 255 *  width/MAX;
   scaled8 = uint8(scaled);
    imshow(uint8(scaled));
    level = graythresh(scaled8)
   BW = im2bw(scaled8,level);
  figure(2);
  imshow(BW)

Doesn't make sense to me.

[Walter Roberson]

My code worked when I tested it on some test data:

width = ndgrid(0:500,0:50);
MAX = 500;

[Image Analyst]

Douglas, what is "width"? It's not a scalar is it? It's a 2 or 3-D image, right? Otherwise scaled will not be an image - it will just be a single number.