% coverage

S
Posted By
skorvin
Nov 2, 2003
Views
495
Replies
8
Status
Closed
can i use photoshop
to calculate the % of pixels of a defined color in an image (or grey treshold…) ?

or is there some other program who can do this ?

k

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BV
Bart van der Wolf
Nov 2, 2003
"skorvin" wrote in message
can i use photoshop
to calculate the % of pixels of a defined color in an image (or grey treshold…) ?

Yes, sort of.
You select by color, and read the histogram for the number of pixels in the selection. Then divide by the total number of pixels. It can be done, but it’s cumbersome if you need to do it a lot.

Bart
S
skorvin
Nov 2, 2003
"Bart van der Wolf" wrote in message
"skorvin" wrote in message
can i use photoshop
to calculate the % of pixels of a defined color in an image (or grey treshold…) ?

Yes, sort of.
You select by color, and read the histogram for the number of pixels in
the
selection. Then divide by the total number of pixels. It can be done, but it’s cumbersome if you need to do it a lot.

Bart

the purpose i have:
water sensitive paper turns blue with contact with water i would make a high res scan and i would like to know the % coverage with blue
any other suggestions ?

k
JC
J C
Nov 3, 2003
On Sun, 2 Nov 2003 16:05:29 +0100, "skorvin"
wrote:

the purpose i have:
water sensitive paper turns blue with contact with water i would make a high res scan and i would like to know the % coverage with blue
any other suggestions ?

k

It would seem to me to be quicker to just measure the area and calculate the percentage of the total area turned blue.

Rather than scan the thing, a simple ruler sounds like a better method. But then your descriptions is a bit general so I’m might be missing something.

What practical application does this paper have?

— JC
C
cloggy
Nov 3, 2003
After having spent 40 days and 40 nights pondering the subject, the best J C could come up with in comp.graphics.apps.photoshop was this:

On Sun, 2 Nov 2003 16:05:29 +0100, "skorvin"
wrote:

the purpose i have:
water sensitive paper turns blue with contact with water

<snipped>
What practical application does this paper have?

— JC
its used, for example inside cell phones, laptops and other devices, so the manufacturer can see if the item has been dropped in water and then dried out (usually not covered under warrenty)

hth

BTW, best thing is just to buy a new piece of paper and swap it over if you have dropped yer fav piece of hardware in the bath/pool/toilet ;0)


************************************************************ ********** cloggy a.k.a. Max a.k.a. That drunken fat bloke who just stole my beer "a certified ignorant f**k"
you know if it ain’t broken, you just ain’t trying 🙂
************************************************************ **********
J
JD
Nov 3, 2003
Anyone know of a plugin to open Canon RAW files for PS version6 ? AJ

"skorvin" wrote in message
can i use photoshop
to calculate the % of pixels of a defined color in an image (or grey treshold…) ?

or is there some other program who can do this ?

k

BV
Bart van der Wolf
Nov 3, 2003
"AJ" wrote in message
Anyone know of a plugin to open Canon RAW files for PS version6 ? AJ

You can do it for free with IrfanView (http://www.irfanview.com/). Make sure you also download the Canon CRW plug-in for it from the same site.

Bart
S
skorvin
Nov 7, 2003
"J C" wrote in message
Rather than scan the thing, a simple ruler sounds like a better method. But then your descriptions is a bit general so I’m might be missing something.

What practical application does this paper have?

it’s purpose is the determination of spray patterns and measuring spray drift (when apllieng pesticides)

k
JC
J C
Nov 8, 2003
On Fri, 7 Nov 2003 19:37:00 +0100, "skorvin"
wrote:

it’s purpose is the determination of spray patterns and measuring spray drift (when apllieng pesticides)

k

Then I’d guess that a lot of sheets of this paper are going to be placed in a field. Then the sheets collected and measurements taken.

Wouldn’t it be easier to simply measure the amount of the chemicals on the paper using standard lab procedures?

— JC

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