Chroma key / green screen

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• hgy29 Maintainer

  January 2017 Accepted Answer

  Possible using the camera plugin and a shader

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• totebo Member

  January 2017

  Nice one, I should have guessed!

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• hgy29 Maintainer

  January 2017 edited January 2017 Accepted Answer

  For the record:

  require "camera"   local ChromaKeyVShader= [[ attribute vec4 POSITION0; attribute vec2 TEXCOORD0;   uniform mat4 g_MVPMatrix;   varying mediump vec2 texCoord;   void main() { gl_Position = g_MVPMatrix * POSITION0; texCoord = TEXCOORD0; } ]]   local ChromaKeyFShader=[[ uniform lowp sampler2D gCam; uniform lowp sampler2D gTexture; varying mediump vec2 texCoord;   #ifdef GLES2 precision mediump float; #endif   mediump vec3 rgb2hsv(vec3 c) { mediump vec4 K = vec4(0.0, -1.0 / 3.0, 2.0 / 3.0, -1.0); mediump vec4 p = mix(vec4(c.bg, K.wz), vec4(c.gb, K.xy), step(c.b, c.g)); mediump vec4 q = mix(vec4(p.xyw, c.r), vec4(c.r, p.yzx), step(p.x, c.r));   mediump float d = q.x - min(q.w, q.y); mediump float e = 1.0e-10; return vec3(abs(q.z + (q.w - q.y) / (6.0 * d + e)), d / (q.x + e), q.x); }   void main() { lowp vec4 colorTex = texture2D(gTexture, texCoord); lowp vec4 colorCam = texture2D(gCam, texCoord); vec3 hsv=rgb2hsv(colorCam.rgb); gl_FragColor=colorTex; if ((hsv.x>0.7)||(hsv.x<0.5)||(hsv.y<0.5)||(hsv.z<0.1)) //Filter-out non blue-ish colors gl_FragColor=colorCam; } ]]   local ChromaKeyShaderAttrs= { {name="POSITION0",type=Shader.DFLOAT,mult=3,slot=0,offset=0}, {name="vColor",type=Shader.DUBYTE,mult=0,slot=1,offset=0}, {name="TEXCOORD0",type=Shader.DFLOAT,mult=2,slot=2,offset=0} }   local ChromaKeyShaderConstants={ {name="g_MVPMatrix",type=Shader.CMATRIX,sys=Shader.SYS_WVP, vertex=true}, {name="gCam",type=Shader.CTEXTURE,mult=1,vertex=false}, {name="gTexture",type=Shader.CTEXTURE,mult=1,vertex=false}, }     local ChromaKeyShader= Shader.new( ChromaKeyVShader,ChromaKeyFShader, Shader.FLAG_FROM_CODE,ChromaKeyShaderConstants,ChromaKeyShaderAttrs)   local camTex=Texture.new(nil,1024,1024) Camera.start(camTex,application:getDeviceHeight(),application:getDeviceWidth()) local scrw,scrh=application:getContentWidth(),application:getContentHeight() local camview=Mesh.new() camview:setVertexArray(0,0,scrw,0,scrw,scrh,0,scrh) camview:setTextureCoordinateArray(0,0,1024,0,1024,1024,0,1024) camview:setIndexArray(1,2,3,1,3,4) camview:setTexture(camTex) camview:setTexture(Texture.new("back.jpg",true),1) camview:setShader(ChromaKeyShader) stage:addChild(camview)

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