Analyzing NDVI Imagery Using Blender

Analyzing NDVI Imagery Using Blender

Hideki Saito

September 8, 2014

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Contents1 About This Research 2

1.1 Companion Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.2 License . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2 Motivation 2

3 Process 3

4 Outcome 3

5 Further Improvements 4

6 Yet Another Improvements 5

7 Version Similar to Infragram.org Output 87.1 Some Examples From My Yard (and Surroundings) . . . . . . . . . . . . . . . . . . . . . . . . 10

8 Conclusion 128.1 Next Step . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Abstract

Blender is a Free Software for 3D modeling and rendering. The software also contains an extensivesuite of image adjustments and composition. The aim of research is to explore the methodology ofgenerating pseudo-color imagery using the Blender image compositor system.

1 About This Research

1.1 Companion FilesData files for this research is available at the following Public Lab research note page:

http://publiclab.org/notes/unsignedint/08-27-2014/analyzing-ndvi-imaginary-using-blender

1.2 LicenseThis research is licensed under Creative Commons Attribution-ShareAlike 3.0 Unported License.

2 MotivationUsing Blender[2] software, I have attempted to create node settings that allow researchers easy and efficientway to generate a composite image for NDVI imageries.

The advantage of this setting includes:

1. The software is free, and runs on various platforms

2. It’s easy to adjust individual components, such as color maps, as well as channel adjustments.

3. Image files can be packed into single “blend” file. Research can send others one file containing thecomplete set up of the original researcher. (“Lab in a file”)

4. Processing movie files or set of image sequences (such as time lapse) is no harder than processing astill image.

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3 ProcessFirst, for this example, I have used an image that came with a Infragram point-and-shoot camera. (MobiusActioncam)

This file was named example-before-processing.jpg. I wanted to plug this into Blender process, thereforeI have imported this image into Blender, using a input node.

The process pass is as follows. (Please see the attached .BLEND file for details.)

1. Image input is separated to RGBA, breaking B component, connecting the rest to RGBA combiner.

2. I have applied color map, I have tried with Ned’s protanopia-friendly lut[4] as a color map for thisexample. I have also included a color ramp using one of the examples in the New NDVI colormap[1]

3. Finally coloring is mixed, 50/50, coming from “GB” component of the image, as well as “B” componentmapped to the color ramp – balance for this component can be adjusted to fit your need, too.

4 OutcomeI have obtained the following result using this process.

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5 Further ImprovementsI have further investigated better separation of the needed component, by subtracting R component (visiblelight) from B, to filter out visible light portion of the image, which provided the sample below.

This could be mapped to the color scale:

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Better separation also allows me to composite the result better to the visible light, which may be appro-priate for identifying possible vegitation activities.

6 Yet Another ImprovementsI have combined NDVI processing into group node – which (hopefully) doing the NDVI processing correctlybased on the formula of NDV I = (IRR)

(IR+R) .

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7 Version Similar to Infragram.org OutputInfragram.org[3] provides web based conversion, the setting could be further adjusted to provide the outputsimilar.

This can provide three types of output, similar to Basic, Colorized, and combined (basically Colorizedformat overlain by visible light – no Stretch and Fastie colormap, yet)

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7.1 Some Examples From My Yard (and Surroundings)

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8 ConclusionBlender has a potential to efficiently process image NDVI images for various applications. I would like toexperiment with it further to improve the process further.

8.1 Next StepI am still new to NDVI, having just received the camera a day ago. My future attempts, including tryingthe process using additional images as well as trying better color ramps and adjustments.

Comments, suggestions and improvements are highly appreciated!

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References[1] cfastie. Public lab: New ndvi colormap. http://publiclab.org/notes/cfastie/08-26-2014/

new-ndvi-colormap. Accessed: 2014-09-08.

[2] Blender Foundation. blender.org - home of the blender project - free and open 3d creation software.http://www.blender.org. Accessed: 2014-09-08.

[3] Public Lab. Infragram: online infrared image analysis. http://www.infragram.org/. Accessed: 2014-09-08.

[4] Public Lab. Public lab: ndvi-gradients. http://publiclab.org/wiki/ndvi-gradients. Accessed:2014-09-08.

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