The [Infragram Sandbox](http://infragram.org/sandbox) is a browser based tool for experimenting with image compositing, intended for use with Public Lab [Infragram cameras](/wiki/infragram). Read [this research note](/notes/warren/08-17-2013/infragrammar-compositing-infrared-images-with-simple-mathematic-expressions#c6664) and watch this short video to get a quick idea of how to use it: ##Infragrammar Infragram Sandbox uses simple math expressions, which are actually written in JavaScript. Here are some examples: * [NDVI](/wiki/ndvi) = `(R-B)/(R+B)` for -1..1, or for 0..1 `(((R-B)/(R+B))+1)/2` in the Monochrome input * ENDVI = `((R+G)-(2*B))/((R+G)+(2*B))` which MaxMax uses for its vegetation stress cameras, in the Monochrome input * A colormapped NDVI, scaled to emphasize differentiation: `((R-B)/(R+B)-0.2)*-720`, in the Hue input, and tweaking the 0.2 value to between 0.1 and 0.9 ([read more here](/notes/warren/08-24-2013/infragrammar-with-hsv-color-model)) * (add yours here) ###Math Infragrammar can use [JavaScript math functions](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math). These include: * `Math.log()` - logarithms * `Math.abs()` - absolute value * `Math.sin()` - sine ###Sliders You can also link an equation to a slider; for now we are using the letter "X" to represent this value, but in the future, any string represented as {mystring} will generate a slider called "mystring". Move the slider to try different values in real time. [](http://publiclab.org/system/images/photos/000/001/174/original/Screen_Shot_2013-08-17_at_11.52.00_AM.png)...
| Author | Comment | Last activity | Moderation | ||
|---|---|---|---|---|---|
| mathew | "this is really cool. I made mine out of paper and tape " | Read more » | over 10 years ago | |||
| mathew | "I'm surprised at the IR passing of the Powershot. nice research. really should buy some of those NIR LEDs myself. " | Read more » | over 10 years ago | |||
| cfastie | "Is the levels stretching you are referring to the same thing as histogram stretching? If so, it should be high priority. If the look up table feat..." | Read more » | over 10 years ago | |||
| warren | "As i pointed out in the comments here yesterday, this HSV approach is pretty interesting and conceptually fun, but not ideal for real work with LUT..." | Read more » | over 10 years ago | |||
| warren | "Corrections made re: order of operations, thank you Chris for a sharp eye and a clearer memory of how to do basic arithmetic! And you said you coul..." | Read more » | over 10 years ago | |||
| warren | "Mathew only sent me one raw image: " | Read more » | over 10 years ago | |||
| cfastie | "It looks like you've done a good job matching the NDVI index from the two cameras. It's hard to evaluate the meaningfulness of the NDVI images beca..." | Read more » | over 10 years ago | |||
| nedhorning | "I think it might be possible to work on a simple calibration process that could be used to get decent NDVI values. I don't think there is much a us..." | Read more » | over 10 years ago | |||
| mathew | "This isn't working for me either. I get a red or blue image, but not a NDVI-style color map. " | Read more » | over 10 years ago | |||
| warren | "...the plant pixels will have the biggest values for both R and B and the difference between them is therefore likely to be bigger. Yeah, the idea..." | Read more » | over 10 years ago | |||
| PeeBee | "Thanks cfasie. I understand now the exposure issue you raise. But you seem to assume the different exposures are an unknown, which it strikes me ..." | Read more » | over 10 years ago | |||
| cfastie | "To compute NDVI, you have to know the relative amount of light in a visible and an NIR band being reflected from plant leaves. The difference betwe..." | Read more » | over 10 years ago | |||
| air_maiden | "I too am interested to see whether a non-modified camera and a camera with the IR filter removed can be used to calculate NDVI. Could you please cl..." | Read more » | over 10 years ago | |||
| cfastie | "That's a really clever idea, and I think it might work. However, it assumes that: The photos must be simultaneous if anything in the scene is cha..." | Read more » | over 10 years ago | |||
| PeeBee | "Thanks cfastie. I don't think I understand the need for the Wratten filter. My understanding is: A camera with just the IR filter removed (i.e. n..." | Read more » | over 10 years ago | |||
| zorn | "Ah, thanks for the answers! Makes it much clearer now.... As i told before, i want to have the possibility to tae normal Pics and pure NIR.... I ..." | Read more » | over 10 years ago | |||
| cfastie | "I see what you mean when you say that the difference between the blue and red channels is correlated with the presence of plants. Your monochrome i..." | Read more » | over 10 years ago | |||
| cfastie | "Zorn, If you remove the IR block filter, the camera will take very strange photos because all three color channels (RGB) will have lots of NIR ligh..." | Read more » | over 10 years ago | |||
| warren | "In short, while you've clearly shown there is IR in all 3 channels, there is still a reasonably good signal/noise ratio difference between 2 channe..." | Read more » | over 10 years ago | |||
| warren | "Thanks Chris, but I'm not sure I agree that we're just seeing brightness due to infrared. I'm not saying this is NDVI -- it seems to work in the re..." | Read more » | over 10 years ago | |||
| cfastie | "If you have two cameras, and your goal is NDVI or false color infrared, the best way to get what you need is one unmodified camera and one with the..." | Read more » | over 10 years ago | |||
| PeeBee | "I am new to this field, and am busy trying to mod a Mobius by removing the IR filter and adding a blue (red remove) filter. I have made a side by ..." | Read more » | over 10 years ago | |||
| cfastie | "More tests are definitely merited. First, I was assuming that Carl was using a Rosco blue filter, and my original conclusions were based on that. ..." | Read more » | over 10 years ago | |||
| warren | "With the new Infragram.org, Mathew Lippincott and I did a new attempt at using these images and exploring the Mobius as a potential Infragram-modda..." | Read more » | over 10 years ago |