Record the length of the line, in pixels. Right-click on the Eyedropper Tool - located in the left sidebar of the main window, as shown below - and select the Ruler Tool.Ĭlick and drag line segment HwL, such as the sample line shown below. If you don’t know how to measure “HwL” and “HW” then please refer to “ How to estimate instar” for detailed, step-by-step instructions. Use the Photopea “Ruler Tool” to measure the length (in pixels) of two line segments: HwL (Hind wing Length) and HW (Head Width). Note: You should go to File / Open… and navigate to a photo of an odonate larva. In order to make this tutorial as simple as possible I went to the Photopea menu bar, navigated to File / New… and created the default blank white canvas, shown below. Open Photopea in a Web browser: (For what it’s worth, I prefer “Google Chrome.”) Since Photopea is Web-based, it runs on desktop computers, laptop computers, tablets, and smart phones. Photopea is a Web-based clone of Photoshop - Photopea doesn’t do everything Photoshop does but it can be used to make measurements on photos using a workflow similar to the one I described in detail in a blog post entitled “ How to estimate instar.” “ Photopea” is a free alternative to Adobe Photoshop. Does that mean you’re out of luck if you don’t? In a word, no. The process works well, that is, as long as you have Photoshop. In two recent blog posts (see Related Resources, below), I showed how Adobe Photoshop can be used to make measurements that enable you to estimate the instar of odonate larvae (nymphs).
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