---
title: Take a photo and remove greenscreen with JavaScript
slug: take-a-photo-and-remove-greenscreen-with-javascript
published_at: 2021-03-29 17:00:03 +0000
updated_at: 2026-03-04 20:14:21 +0000
summary: 
description: In this episode, we show how to take a photo with the browser, then remove the greenscreen by either setting alpha to 0 or by replacing the pixels in the background with a specific color.  Code: https://github.com/cjavdev/video_automation Twitter: https://twitter.com/cjav_dev Feedback: https://forms.gle/Q31hhjJGsMrvY4mL6  It turns out there's a really excellent tool called TubeBuddy that already exists and does most of what I was planning to build. I've started using TubeBuddy in the past few months and really like it. If you use this link to buy a license, I'll get a small cut for being an affiliate: https://www.tubebuddy.com/cjavdev.
tags: [Take a photo and remove greenscreen with JavaScript, remove greenscreen with JavaScript, remove greenscreen from photo, remove greenscreen from picture, greenscreen removal in JavaScript, greenscreen removal in JS, JavaScript, greenscreen, chromakey, chroma key, chromakey in JavaScript, Remove green background with JavaScript]
views: 2716
author: CJ Avilla
url: https://www.cjav.dev/videos/take-a-photo-and-remove-greenscreen-with-javascript
youtube_url: https://www.youtube.com/watch?v=6cwsNpvp6vo
youtube_id: 6cwsNpvp6vo
embed_url: https://www.youtube.com/embed/6cwsNpvp6vo
thumbnail_url: https://i.ytimg.com/vi/6cwsNpvp6vo/hqdefault.jpg
type: video
---

# Take a photo and remove greenscreen with JavaScript

*Published: March 29, 2021*
*Views: 2716*

## Watch

[Watch on YouTube](https://www.youtube.com/watch?v=6cwsNpvp6vo)

[![Take a photo and remove greenscreen with JavaScript](https://i.ytimg.com/vi/6cwsNpvp6vo/hqdefault.jpg)](https://www.youtube.com/watch?v=6cwsNpvp6vo)

## Description

In this episode, we show how to take a photo with the browser, then remove the greenscreen by either setting alpha to 0 or by replacing the pixels in the background with a specific color.

Code: https://github.com/cjavdev/video_automation
Twitter: https://twitter.com/cjav_dev
Feedback: https://forms.gle/Q31hhjJGsMrvY4mL6

It turns out there's a really excellent tool called TubeBuddy that already exists and does most of what I was planning to build. I've started using TubeBuddy in the past few months and really like it. If you use this link to buy a license, I'll get a small cut for being an affiliate: https://www.tubebuddy.com/cjavdev.

## Transcript

hey friends today in this episode i'm going to talk about how to take a photo using the browser and javascript and then apply a green screen chroma key so here i'm just like showing what uh what this looks like in screenflow which is the video editing software that i use for these videos and there is a tool in the video filters tab where you can click plus and then add a chroma key video filter and that just like removes the background so you can see what's behind it and there are a couple of controls here there's the white clip which changes whether or not you display or like what the transparency of the pixel looks like there's also this like tolerance tool that allows you to modify and tweak and then some angle feature and then you can also just like sort of like refine the key so that it is like the perfect color green um and so this is this is really really helpful for video and one of the things that we've been doing with the video description manager series is working on tools for building thumbnails so if you recall we are working on a rails app here that helps us automate parts of the video production process specifically for putting up content on youtube and so one of those things that i want to do is to make make some improvements to our tool um that allows us to create and generate thumbnails so here we have like a list of videos and if we go to a specific video and then like slash thumb then we can generate a thumbnail and upload that thumbnail directly to youtube this is being generated based on some metadata about the about the uh the video so the title is being pulled the category categories being pulled and then this image here that's on the right was just a single green screen image that i took and then applied the background to make it the same sort of color as this and what i want to do today is make it so that it's really easy to just take a green screen photo of what you sort of like look like on the day you're recording and then uh use that as part of your thumbnail and so uh yeah let's just talk about how we might implement that so i'm gonna say rails g thumbnail uh let's see controller thumbnail headshots controller and we're going to use the new action now most of the content today is going to be javascript we're not actually going to do much with rails but we are doing this in the context of a rails app so if we go to the thumbnail headshots uh new view here and then we're just gonna like work in here so let's say uh take a new uh headshot all right so what i think we need is some video a video input so we're going to collect the video stream from the browser so we're going to ask for permission collect the video stream from the browser and then put that into a video control and then we'll use the html canvas so we'll like take uh we'll let's add a yeah so let's add a button um and the button will have like an id of like capture or something capture and we'll say capture and then we need a video input control so let's actually wrap this in a div just because that'll be on a new line and then we'll need a video input and its id will just be like a preview or something and we'll give it a height of 10 80 and a width of 1920 and um let's see so what does this actually look like here so let's let's write some javascript uh let's see so we're gonna have a script tag and we want to grab reference to both of these things so that we have uh our capture button and we have our um our video preview preview video preview okay now the next thing we need to do is like grab the stream grab the video stream um from the user and i think we want to do this when the page is like fully loaded so let's say document.um add event listener for dom content loaded and we'll use this so that we can write uh like use async await in here but also like so that everything is loaded in the dom when we're ready to go okay so we want to get the stream out of that media input that's coming in so we're going to say cons stream is equal to await navigator dot media devices dot use and this is a function that takes in an object which just has like audio true and video true actually we don't even need the audio because we're just doing um we're just doing a camera input this time and then the next thing we want to do is set that stream as like the source object for our preview video so preview video dot source source object equal stream i think that's how it works all right let's see if this is actually firing up so if we go to like slash thumb thumbnail headshot slash new we have a capture button but we don't actually have a video here so what's happening here let's open the console and see if we have any errors what's going on so i see the little red dots suggesting that our camera input is working let's just give it a style of border px solid black just so we can see if it's actually on the page okay so it's totally there and then the next thing uh you know what i think i missed is uh auto play and uh let's refresh okay cool so there it is it's auto playing and this is the input i do have a green screen um over here on the left i've got like a chest of drawers and there's like some pictures up there this is going to be helpful i actually want this in this shot so we can see the difference as we're sort of like removing the green screen and show that that like actually won't be removed by default and that's right that's correct um so the the camera input is 1920x1080 and i want to keep that sort of aspect ratio and so it's going to be kind of big and messy so i want to make this capture button just a little bigger just so we can this is sort of totally hacking it so that we can see the button easier um i'm just going to put this font size up to like 5 em or something just to get it to be a huge picture so that we can make the page smaller and see everything on the page okay so the next thing that we want to do is when we click the capture button we should create a canvas here and the canvas element should be populated with whatever like the shot was the screenshot was so let's do that next so let's add a click to our capture button a click handler to our capture button there that we have and then what we want to do is we want to um let's actually create we can create a canvas up here also so we'll say canvas and we'll give this an id of like a photo or something and it'll have the same height and width and we don't need any style i don't remember if video if the video element works as a single line tag my editor seems to think that's how it should work all right so let's grab reference to the photo canvas photo and then we'll we'll also yeah let's just um gra create the context here too so const photo um ctx is photo canvas dot get context uh 2d all right so now we have reference to the context for that canvas and what we should be able to do is when the when the button is clicked we should be able to say something like photo ctx dot draw image with the preview video as input and we'll draw it at zero zero and then we also need to pass in the the width and the height which we can pull off of that preview video so we're going to say like const the client width is w and the client height is h and we'll pull that off of preview video so this is using object destructuring with an alias so i'm aliasing the client with this is sort of the same as saying like const w equals preview video dot client width which is i don't know it's just like shorthand but let's let's see if this works so when we click capture nothing happens okay and we do have an error so capture button is not defined capture did i spell it wrong capture btn cap capture btn all right capture btn in programming almost always the issue is uh spelling okay sweet look at that okay so if we click capture it takes the picture that's like exactly what we want right and now we need to play around with this photo to see if we can get it to remove the green screen so that we can just have like an image that has um no green screen in the background so how does that actually work well if we were to zoom in like insanely far here right uh each of these little um dots that make up this picture are a combination of four four data points it is a red green and blue value and then also an alpha so if we're looking at like um a color in css right over here if we were to find if we go to the elements tab and we go to computed and we find some color here right we see rgb that's one way to define a color you can also define it as like rgba so if we if we grab um yeah let's grab one of these and just say style h1 and we'll say color is rgba and then call it a function where we can pass in like one two three and then two five five or something right that will create a very dark color because zero zero zero zero is black and if we if we change this to all two fifty fives um that will make it white two fifty five that makes it a white color right and so this is like your rgba colors if we were to drag this into the green spectrum and then start playing around up here what you'll see is that like the green value is very high the r value is low and the b value is low so when we're looking at a very green color the combination of red and blue is likely less than the green so in this case 28 plus 52 is i don't know roughly 80 and that is less than 204 so even even if we go into like some of these colors that are like pretty dark green right we still get pretty close to having um you know the red value plus the blue value being less than the green the total green value uh and then over here we have alpha so alpha is what allows us to like control the transparency and it goes from zero to one usually this is controlled as a number between zero and 255 that's like how they get from zero to one um but whatever so let's let's uh let's see if we can analyze this image data as like more of a more raw data format so um this photo context object has a method for getting the image data out of it so we can say image data is equal to a photo ctx dot get image data i believe it's called and let's just console dot log image data let's see if this actually works filled to execute four arguments required only zero present okay so i think we actually do need to pass in um the the corner like the top left corner in the bottom right corner uh when we're getting the image data so let's see if this works so now if we click capture okay cool so now we have an image data object down here um and the image data object has three properties it has height width and data data is a giant array uh a uint8 clamped array so it's a it is an array where uh yeah it has unsigned unsigned 8-bit integers so down here you'll see that we have these these are like the first four elements in the array and that represents probably this top left corner maybe the bottom right corner i can't remember which corner this is but you'll see that like this is the r g b value and then this is the alpha so alpha meaning like don't make it transparent at all show like the entire possible value so if this was zero then it would be like a transparent pixel but instead we have like a low red value a high green value in a low blue value so this means that this pixel that is represented by the first four elements in this array is very likely going to be a green pixel and so what we want to do is iterate over all of this image data and convert the the final value here of these four of like the this four sum it's like a tuple but there's four in it i don't know uh into zero to like remove the background so let's see if we can do that so we want to iterate over all of the data remember that this image data object has a data property it's not like itself data so we want to we want to say something like for uh i will start at zero while i is less than image data.length divided by well yeah image data.length we'll just go through um and let i increase all the way to the end of the image data's data length and the way that we'll step through it is because because each chunk is four long we'll just say like i plus equals four and so we will iterate this is going to allow us to iterate through each of those chunks and so if we say that like const g so the green value is image data.data at i plus 1 i think that's right right rgb rgb rg yep so when when i is 0 then i plus 1 is going to be 1 and that should be this value so that's the green value so then if the green value is greater than i don't know 100 then let's say image data.data at i plus three is equal to zero so that should just like remove or clear out or it should set the alpha to zero which will make that pixel transparent rather than being like a color so if we refresh the page here and click capture uh nothing happened okay uh oh right because after we've made that change we need to like update the we need to update the the canvas so let's say photo ctx dot put image data and we're gonna put in the new image data here and let's just try this uh i don't know if it's gonna let me okay yeah i let's see three arguments required but only one present so i think maybe we just have to tell it where the top corner is oh look at that okay sweet so we've totally removed all of the green values including anything that had red or pink or white or anything else like you can even see like sort of parts of the green that were in the yellow on the shirt are also removed here right and like in fact we still have some green that was left in so one way that we can approach this is we could say like let's try to fine tune it so that g maybe like g is great only do it if g is greater than 200 and we can refresh the page and click capture and it gets like it changes which pixels are being removed but you'll notice that in this case right we removed less incorrect pixels but we still have like some that's definitely like whiting out the face and so if you recall right when we were looking at um maybe saying like the color is green oh let's see uh our rgb um 0 255 0 0 rgba right and then if we click on this thing and then let's make this one right like most of these colors are where where it's green is a combination of red and blue is less than or equal to the green value so what we can do is say if green is greater than um red and blue then set it to uh or then clear it out so let's let's do that so um so the red value is actually just going to be at i green is at i plus one and then blue is going to be at i plus two rgb okay so then if we refresh the page here and say capture that is pretty close right that's pretty close like you still can see um you can still see a little bit of uh green around the face right uh so we can play around with this tolerance just a bit so let's add let's add an input box next to our capture button um but or let's say input text or yeah type is a number and we'll just call this uh tolerance or something and then yeah we'll give it a font size is like 5 em so uh oh gosh that's it's so hacky okay so let's say our tolerance number is uh by default uh value is uh 10 or something and then we'll say like if green is greater than red plus blue let's grab our tolerance here is it called yeah it's called tolerance yeah okay so then here then we can say that like when the button is clicked we'll extract our const uh tolerance value is tolerance dot value and we'll parse this into an integer parse int okay and then we'll say minus tolerance value so like if the combination of red and blue minus the tolerance value is greater than green then we should be good to go so if we click capture here when it's 10 we see that like uh it's taking away a little bit more than we want if it's negative 10 what does that look like okay so that that put back in my armpit but it didn't um it didn't really like clear around the the face there so what if we go to like negative 100 okay that leaves in too much negative 50. all right that takes out too little positive 50. that takes out too much so if we go to zero that's actually like pretty close to what we want right and now like the next step would be um we either we could either like try playing around with uh the angles and the uh some other some other things here right like um the white clipping and the angle and the tolerance a bit more but instead what i think i'm going to do is just like save this and use this and then i think this might be good actually the other thing that that we could do is that like when we're taking the screenshots or when we're taking the the photos for the thumbnail oh also you can just like save you can say save image and that'll download it as whatever png that you want for your thumbnail so one one thing that we did for our thumbnails is if we if you recall and we go back to categories uh so categories have a title color in a subtitle color we could even add like a background color or something right so let's let's let's do that where we can um instead of just setting the transparency to uh instead of just setting the transparency here let's instead accept as an argument a color that we want to use as the new background that we're going to replace the background with so let's do that here so the type is going to be color bg color and it's not going to have a value to start with and then we'll we'll need to work with that color so i have never actually worked with with color objects before so this is going to be interesting this will be fun to figure out so like if we come back over here and here's our little color picker thing gosh this is uh all right it's hard to see okay so this gives you rgb values let's say that we want it to be um let's see okay yeah so this is this is too small um all right so if we wanted our background color to be some bluish or purple color or something right like theoretically we should be able to click capture here and when we capture we should have access to this color object in the terminal so we have um oh let's yeah let's uh let's grab a reference to the color um the color input so color input is going to be bg color and then down here we'll just like console.log bg color our color input color input okay so then when we click capture we get the color input thing okay but let's uh let's see if we can okay so i'm going to add a break point on line 49 and then i'm going to pick a random color here so we'll just say something like that and then we click capture so color input dot value what does that give us okay so it gives us the hex value all right so color input dot um can we get some sort of like rgb value or something red no rgb let's see how to get rgb value from color input i wonder if we need to like oh here we go let's see color wait uh value dot red no uh on change pick red wow okay so you do you have to like parse it into a uh you have to parse it into hex values um okay yeah we can totally do that we can totally do that uh sure um wow i'm surprised that's like how you have to do it but whatever all right so let's say we get the value and dot string um yeah yeah yep yep yep substring zero two one and one two three all right so so we're gonna say like uh const bg red is this one um green is this one and blue is this one and this will be like four to six and seven to nine i think maybe console.log bgr bgg bgb and the idea is that like we should hopefully be able to just like reset the color to whatever we want um nope okay so uh actually let's see what did we get what is the value the value is all zeros uh that's not helpful let's make it something where the numbers are different okay there we go sure capture um capture color input dot value okay so we're looking for 0 1 4 5. oh interesting oh four to six no so we want five to seven because the next number that we want is zero eight so three two five okay so it's it's not inclusive that's weird okay so three five five seven all right let's see if we can get this sorry i i like looked at the stack overflow post but then i didn't actually like pay attention to it um okay so then let's say that's our our number and okay so we've got 23 86 d1 and 23 86 d1 okay so those are like the components right of the hex values now we need to convert them into integer values because d1 isn't an integer right so d1 this is the base 16 value which represents what that color is so we can use parse int so down here we used parseint and we did not pass in a base that's because the default base here is 10 because it assumes that we're talking about decimal but in this case we're talking about hex so we need to do a parse int and then we need to pass in 16 because we're using base 16 now right so now we should be able to take our rgb values and use those instead of using alpha right this is uh like remove the pixels and this one is going to be like set the pixels as the background pixels so we need to put uh we need to set um yeah we'll we'll set the alpha to 255 so that it's always fully visible it might it might i mean it should already be that but whatever um and then this is one two and then so this is going to be this is going to be the r the background r value this is going to be the background green value and the background blue value all right so let's see let's see if this works uh i have a feeling it it might i don't know so we're going to say that's our background color if we click capture and remove our breakpoint oh that's so cool so if our background is uh i don't know this blue color capture so cool awesome so this should like when you and when you're looking at the image here right like before the green didn't seem like it was being taken off but we were looking at it with a white background and now for switching the background to a different color it's much more challenging to tell um to tell like whether or not that tolerance is super important or not um and then the other thing is that that's interesting is that we can like we can sort of use um we can we can change what input type i think we want here so if we know if we know the color that we want so like let's say i don't know uh dead beef right like let's say that's our color and then we capture and that ends up being our background so uh pretty cool i think i'm happy with this and we can call it good there and then yeah hopefully this was useful and interesting um and uh yeah all right so that is how you might take a green screen image in javascript as a quick recap if we look back at our code here we we grab reference to a ton of different elements that we threw on the page one of them being a big button to capture the photo we then also entered a tolerance number and a color input and then we had a video control which was our preview that was just showing us like ourselves it's kind of like a mirror then we had a canvas where we were actually like rendering the frame for the video when we took the picture and what we did was we said that like we're going to set up that video input and update our that the video to be our preview and then when the button is clicked when that preview button is clicked we're gonna like figure out what the background color should be based on that color input and then we're uh we go through the process of like grabbing an individual image at that point when we're when we're doing the capture we iterate over the image and then depending on if the background is a green screen or not based on our tolerance and the red and blue values then we either remove the pixels with alpha by setting the alpha to zero or we update our our image data to have the the background colors that we selected and then finally we update that context so that it has the image data that we we entered cool if you found this video useful and i hope you did then please it would mean a lot to me if you gave it a quick like i really appreciate you watching and would love to know what kind of content you want to see in the future are you liking the rails stuff you liking the javascript stuff other languages asp.net or c-sharp or go or python or whatever yeah would absolutely love to make some content that's useful to you so um with that said i'm uh my dms are open on twitter if you want to hit me up at cgive dev i would love to chat um yeah just super curious what folks are building out there and would love to help until next time i'll see you later

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