Telling the difference between color and grayscale image

[snibgo]

My Gray scale image has colors in it but i need to have some short of way to figure out it is gray scale image.

That doesn't make sense. How can a grayscale image have colours?

Please show an example image. Also say what version IM you use, on what platform.

[fmw42]

I suspect he means that his image is mostly gray shades, but contains a little color. But I would agree, it would be nice to see an example.

[divptl]

Sorry but i can't share images as it's company's patent . Basically i have patent of say shirt mostly in black and white but say in the pocket of it there is rose picture from IM sample. I need to separate this image from actual normal color picture.

[fmw42]

See viewtopic.php?f=1&t=14807#p148608

[divptl]

Thank you.

Any way to tell if its graphic vs picture ?

[fmw42]

Picture usually has many more colors. Graphic often has only a few. The only way of getting such information is from the histogram or from the number of unique colors.

This will give you a list of colors:

Code: Select all

convert logo: -depth 8 -unique-colors txt:

This will give you the number of colors (unix syntax)

Code: Select all

convert logo: -depth 8 -unique-colors txt:- | tail -n +2 | wc -l

256

However, there is no guarantee that you would not have a picture with only a few colors or a graphic with lots of colors.

[divptl]

if i want to check for gray scale in border (all 4 sides of the image) of the image is it possible ?

[fmw42]

crop the border edges one at a time and check with the saturation as described earlier.

[divptl]

Is there a way to do this same logic for Border only ? I am sorry for being pain but there are way too many fallout so i am thinking to go based on border of picture.

[divptl]

Sorry i didnot see that message . How do i corp and check for the colors at the same time . say 2% of the picture is my border.

[fmw42]

Read my post above: It says, crop the border edges one at a time and check with the saturation as described earlier. For example:

Code: Select all

convert image -gravity north -crop 100x10% +repage -colorspace HCL -channel green -separate +channel -format "%[fx:100*mean]\n" info:
convert image -gravity east -crop 10x100% +repage -colorspace HCL -channel green -separate +channel -format "%[fx:100*mean]\n" info:
convert image -gravity south -crop 100x10% +repage -colorspace HCL -channel green -separate +channel -format "%[fx:100*mean]\n" info:
convert image -gravity west -crop 110x100% +repage -colorspace HCL -channel green -separate +channel -format "%[fx:100*mean]\n" info:

That will test each border of 10% thickness.

[divptl]

Picture usually has many more colors. Graphic often has only a few. The only way of getting such information is from the histogram or from the number of unique colors.

This will give you a list of colors:

Code: Select all

convert logo: -depth 8 -unique-colors txt:

This will give you the number of colors (unix syntax)

Code: Select all

convert logo: -depth 8 -unique-colors txt:- | tail -n +2 | wc -l

256

However, there is no guarantee that you would not have a picture with only a few colors or a graphic with lots of colors.

what is the syntax for windows for "

Code: Select all

convert logo: -depth 8 -unique-colors txt:- | tail -n +2 | wc -l

"

[snibgo]

I would use this instead:

Code: Select all

convert logo: -depth 8 -unique-colors -format %w info:

or:

Code: Select all

convert logo: -depth 8 -format %k info:

[divptl]

how do i do this for all image in DIR and Move the file if it's > threshold ?

[snibgo]

You would write a script.