Chroma+, a new automontage method of image background selection for Insects and other structurally complex objects.

Pavel Jakubec,Martin Novák,Jarin Qubaiová

doi:10.3897/zookeys.795.26870

Abstract

Obtaining taxonomic-grade images is a vital part of probably every present-day morphological study of insects, even though the task itself is perceived as a “necessary evil” due to high investment of both time and effort to produce representable images. Cleaning the background and making it appear as a solid color of known properties is probably one of the most time-demanding tasks. Several techniques have been developed to reduce the time requirement; the most convenient and cost-effective one presumably being the chroma isolation. This method uses a green background that can be isolated and conveniently replaced with another picture or solid color, as used in the film industry. However, the main drawback of this technique is spilling of color onto the object, which is unavoidable and can be corrected only by sacrificing the true color of the object to some extent. Our improved Chroma+ method is based on classical chroma isolation workflow and helps to overcome this problem by taking an additional image of the object with a neutral color background and applying a selection obtained from the chroma-isolated picture on it. This technique is, in terms of the resulting image quality, superior to classical chroma isolation, while the time difference between these two methods is negligible. Furthermore, it does not require any additional equipment (hardware or software), thus being accessible to both employed taxonomists, low budget laboratories, and enthusiasts.

Highlights

A picture is worth a thousand words
To obtain the pictures of our test specimens, we used a slightly modified Canon Cognisys setup (Canon EOS 550D with Canon MP-E 65 mm 1:2.8 1–5× Macro Photo Lens mounted on an automated macro rail for focus stacking (Cognisys StackShot)), which represents a standard setup in the field of macrophotography of insects (Brecko et al 2014)
Chroma isolation represents one of the automated selection methods where the human element is supervising the final result, assisting the computer program only by choosing the appropriate shades of the background that should be selected. Both Photoshop and GIMP offer tools (e.g., Color Range tool (PS) and Select by Color tool (GIMP)) that allow isolation of the background based on a specified color range

Summary

Introduction

A picture is worth a thousand words. This is very true in the field of comparative biology, a scientific discipline, which supports many others like community ecology, conservation biology, pest management, biosecurity, and biological control (Balke et al 2013). The rise of digital cameras opened many possibilities for creating perfect pictures and sharing them with others These possibilities are still expanding beyond new horizons thanks to discoveries of new tools and work-flows. A perfect example of this phenomenon is the focus-stacking technique that enables widening of the available focus depth of the camera This is achieved by merging several pictures with different focus distances together into one final sharp image, bypassing focus depth restrictions posed by the laws of optics (Thomson 2010). Due to these restrictions, it used to be impossible to create sharp images of very small objects (like insect specimens) in their entirety. In the recent years, it has become a gold standard of good morphological descriptions to provide fully sharp image of the specimens that are discussed (Arino and Galicia 2005, Theodor and Furr 2009)

Methods

Results

Conclusion