Histogram of even/odd values

[jhz]

Hi, I want to draw histogram of an image of its just even or odd values. I mean i want to draw graph of values of my choice but not the entire image. is it possible? if yes then please help in the code.

[snibgo]

I want to draw histogram of an image of its just even or odd values.

A histogram records a count of the number of pixels that fall within a certain range of values. For example, if your image has 16 bits/channel/pixel, values are between 0 and 65535. You can have 65536 buckets if you want, with just one value per bucket, but you wouldn't draw that image -- it would be 65536 pixels wide.

[fmw42]

Perhaps he means just even or odd pixels from the image? That could be done by using -sample 50% for one and -roll +1+1 -sample 50% for the the other. I am not sure if -sample 50% starts at 0,0 or 1,1.