#histograms?
3 messages in this thread
I have a weird question. weird in the sense that I am not really sure what it
is I am asking. What it is? HISTOGRAMS. What are they and how do you read
them? I know how to read vectorscopes, osilloscopes, and spectrum anylizers) I
would like to learn more about what they are, and how to read them , for I have
a sneaky suspicsion{msp?}, that I can put that gained knowledge to use.
If anyone can point me to some documentation (preferably downloadable, for I am
lazy, dislike libraries, etc. don't wanna havta research for a day, } it would
be very mucho appreciable.
thanks in advance,
Merlin
Histograms are graphs that plot the spread of light in an image. Think that a
"normal" computer image has 256 different possible values. Black is 0, going up
the scale you have the grays and at the end, or 255, you have white. If you
read an entire image and count the number of occurrence of each value, you have
a histogram. Say, in a 320×200 image, there are 64,000 pixels. Just read one
pixel at a time and increment the [pixel] element of a 256 elements structure.
At the end, you will have the image histogram, or the number of times each
color (gray scale in this example) is present in that image. This is useful to
adjust an image brightness and contrast. You can work with gray scales, RGB,
Chroma and Luminance, and do all kinds of image processing (gamma correction,
saturation, solarization, etc.).
Simply put, Histograms are usually generated by Image Processing programs, and
allow one to graphically see the distribution of grey values (grey scale
images) or color intensities (color images). The Histogram usually plots the
grey or color values in an image against the total number of pixels with those
values….also plots the individual RGB color channels.
With color, the X axis represents color values from darkest to lightest. The Y
axis represents the total number of pixels with the X axis color value. The
histogram usually also displays MAX=total number of pixels in image or area.
VAL=grey value of the graph point under the pointer.
Make any sense ? <g>
BILL