My group has been working on this problem for our own research- extracting leaf area from a photo with ImageJ- and we discovered the following method this week:
***When taking the photo, you need to include an object of known length so that you can set the scale correctly later.*** Open ImageJ. File --> Open --> [Your photo].JPG Zoom in (Image --> Zoom --> In or Cmd + +) until the object of known length is easily visible. Select the *Straight* Line tool from the top menu bar and draw a line along the known length. Zoom out to full extent (Image --> Zoom --> Out or Cmd + -). Analyze --> Set scale… Enter the known length under Known distance and its units under Unit of length. Click OK. Crop out as much of the photo as you can while retaining the area to be measured (Select the *Rectangular* selection tool from the top menu bar and outline the area of interest, then select Image --> Crop or Shift+Cmd+X). Image --> Adjust --> Threshold… Under Thresholding method, select Percentile. Threshold color should be Red and Color space should be HSB. Adjust the sliders under Hue, Saturation, and Brightness until only the desired area is shaded red. Click Select. The area shaded red should be outlined in yellow. Click on the photo. Analyze --> Measure. The area of the selected part of the photo is displayed in a box to the right in the units determined previously, along with the Min/Max/Mean color values for the selected area. Hope this is helpful for you all. -Theo Jass University of North Carolina-Chapel Hill M.S. Geological Sciences, 2015 Coastal Environmental Change Lab http://cecl.web.unc.edu Phone: 641-230-0637 Email: [email protected] 2014-05-21 2:09 GMT-04:00 Surya Kumar Maharjan <[email protected]>: > ImageJ is very handy. I personally have used it to calculate the area of > scanned leaves. > > Cheers, > Surya > > -----Original Message----- > From: Ecological Society of America: grants, jobs, news [mailto: > [email protected]] On Behalf Of Malcolm McCallum > Sent: Monday, May 19, 2014 10:02 PM > To: [email protected] > Subject: Re: [ECOLOG-L] how to measure area with Photoshop > > ImageJ from the NIH works pretty well, or so I've been told. I have not > used it, I used to have an old version of Image tool which predated ImageJ > and it was very user friendly even though intended for microscope work. > > On Mon, May 19, 2014 at 9:41 AM, David Inouye <[email protected]> wrote: > > My brother's been using this technique to measure area by using images > > grabbed from Google Earth. Looks like it might work better for some > > of the areas I've been measuring by walking the perimeter with a > > hand-held GPS > > (Garmin) that can measure area that way. He provided a link to this > > resource for more information about the technique: > > http://blog.duklabs.com/?p=219 > > > > David Inouye > > > > -- > Malcolm L. McCallum, PHD, REP > Department of Environmental Studies > University of Illinois at Springfield > > Managing Editor, > Herpetological Conservation and Biology > > “Nothing is more priceless and worthy of preservation than the rich array > of animal life with which our country has been blessed. It is a > many-faceted treasure, of value to scholars, scientists, and nature lovers > alike, and it forms a vital part of the heritage we all share as Americans.” > -President Richard Nixon upon signing the Endangered Species Act of > 1973 into law. > > "Peer pressure is designed to contain anyone with a sense of drive" - > Allan Nation > > 1880's: "There's lots of good fish in the sea" W.S. Gilbert > 1990's: Many fish stocks depleted due to overfishing, habitat loss, > and pollution. > 2000: Marine reserves, ecosystem restoration, and pollution reduction > MAY help restore populations. > 2022: Soylent Green is People! > > The Seven Blunders of the World (Mohandas Gandhi) Wealth w/o work Pleasure > w/o conscience Knowledge w/o character Commerce w/o morality Science w/o > humanity Worship w/o sacrifice Politics w/o principle > > Confidentiality Notice: This e-mail message, including any attachments, is > for the sole use of the intended recipient(s) and may contain confidential > and privileged information. Any unauthorized review, use, disclosure or > distribution is prohibited. If you are not the intended recipient, please > contact the sender by reply e-mail and destroy all copies of the original > message. > --
