Using Fragment Shaders to Manipulate ImageryMike [email protected] State Universitymjb – January 29, 2013Oregon State UniversityComputer GraphicsOregon State UniversityImage BasicsResTTreat the image as a texture. If you need it, the resolution of this texture can be found by saying:ivec2 ires = textureSize( ImageUnit, 0 );float ResS= float( ires.s);mjb – January 29, 2013Oregon State UniversityComputer GraphicsResSResTTo get from the current texel to a neighboring texel, add±(1./ResS , 1./ResT)to the current (S,T) float ResS= float( ires.s);float ResT = float( ires.t );Image Negativemjb – January 29, 2013Oregon State UniversityComputer Graphics( R, G, B ) ( 1.-R, 1.-G, 1.-B )Image Distortionuniform float uS0, uT0;uniform float uPower;uniform sampler2D uTexUnit;in vec2 vST;out vec4 fFragColor;voidmain( ){vec2 delta = vST - vec2(uS0,uT0);st = vec2(uS0,uT0) + sign(delta) * pow( abs(delta), uPower );vec3 rgb = texture2D( uTexUnit, vST ).rgb;fFragColor = vec4( rgb, 1. );}mjb – January 29, 2013Oregon State UniversityComputer Graphics}0 1(1 )Q t Q tQ= − +Image Un-masking:Interpolation can still happen when t < 0. or t > 1.mjb – January 29, 2013Oregon State UniversityComputer Graphicst = -1.t = 0.t = 2.t = 1.Image Un-Masking:Abusing the Linear Blending Equation for a Good PurposeMore of what Ido wantWhat I have to start with}Blend of what I have and less of what I don’t wantmjb – January 29, 2013Oregon State UniversityComputer GraphicstWhat Idon’t wantto start with0.0 1.0 2.0Iout= (1 - t)*Idontwant+ t*Iin}}Blend of what I have and what I don’t wantdon’t want0 1(1 )Q t Q tQ= − +BrightnessIdontwant= vec3( 0., 0., 0. );mjb – January 29, 2013Oregon State UniversityComputer GraphicsT = 0. T = 1. T = 2.ContrastIdontwant= vec3( 0.5, 0.5, 0.5 );mjb – January 29, 2013Oregon State UniversityComputer GraphicsT = 0. T = 1. T = 2.HDTV Luminance StandardLuminance = 0.2125*Red + 0.7154*Green + 0.0721*Bluemjb – January 29, 2013Oregon State UniversityComputer GraphicsIdontwant= vec3( luminance, luminance, luminance );Saturationmjb – January 29, 2013Oregon State UniversityComputer GraphicsT = 0. T = 1. T = 3.DifferenceIdontwant= IbeforeIin= Iaftermjb – January 29, 2013Oregon State UniversityComputer GraphicsT = 0. T = 2.T = 1.ChromaKeyReplace fragment if:R < TG < TB > 1.-Tmjb – January 29, 2013Oregon State UniversityComputer GraphicsT = 0. T = 0.5 T = 1.Blur Convolution:Blur=242121.16.1Bmjb – January 29, 2013Oregon State UniversityComputer Graphics=121242.16BBlur Convolution:Sharpening=242121.16.1Bmjb – January 29, 2013Oregon State UniversityComputer Graphics=121242.16BIdontwant= IblurSharpeningvec2 stp0 = vec2(1./ResS, 0. );vec2 st0p = vec2(0. , 1./ResT);vec2 stpp = vec2(1./ResS, 1./ResT);vec2 stpm = vec2(1./ResS, -1./ResT);vec3 i00 = texture2D( uImageUnit, vST ).rgb;vec3 im1m1 = texture2D( uImageUnit, vST-stpp ).rgb;vec3 ip1p1 = texture2D( uImageUnit, vST+stpp ).rgb;vec3 im1p1 = texture2D( uImageUnit, vST-stpm ).rgb;vec3 ip1m1 = texture2D( uImageUnit, vST+stpm ).rgb;vec3 im10 = texture2D( uImageUnit, vST-stp0 ).rgb;vec3 ip10 = texture2D( uImageUnit, vST+stp0 ).rgb;mjb – January 29, 2013Oregon State UniversityComputer Graphicsvec3 ip10 = texture2D( uImageUnit, vST+stp0 ).rgb;vec3 i0m1 = texture2D( uImageUnit, vST-st0p ).rgb;vec3 i0p1 = texture2D( uImageUnit, vST+st0p ).rgb;vec3 target = vec3(0.,0.,0.);target += 1.*(im1m1+ip1m1+ip1p1+im1p1);target += 2.*(im10+ip10+i0m1+i0p1);target += 4.*(i00);target /= 16.;fFragColor = vec4( mix( target, irgb, T ), 1. );Sharpeningmjb – January 29, 2013Oregon State UniversityComputer GraphicsT = 0.T = 1.T = 2.Embossingvec2 stp0 = vec2( 1./ResS, 0. );vec2 stpp = vec2( 1./ResS, 1./ResT);vec3 c00 = texture2D( uImageUnit, vST ).rgb;vec3 cp1p1 = texture2D( uImageUnit, vST + stpp ).rgb;vec3 diffs= c00 -cp1p1;mjb – January 29, 2013Oregon State UniversityComputer Graphicsvec3 diffs= c00 -cp1p1;float max = diffs.r;if( abs(diffs.g) > abs(max) )max = diffs.g;if( abs(diffs.b) > abs(max) )max = diffs.b;float gray = clamp( max + .5, 0., 1. );vec4 grayVersion = vec4( gray, gray, gray, 1. );vec4 colorVersion = vec4( gray*c00, 1. );fFragColor = mix( grayVersion, colorVersion, T );Horizontal and Vertical Sobel Convolutions:Edge Detection−−−=121000121H−−−=101202101Vmjb – January 29, 2013Oregon State UniversityComputer Graphics121−101VHS22+=Θ = atan2( V, H )Edge Detectionconst vec3 LUMCOEFFS = vec3( 0.2125,0.7154,0.0721 );. . .vec2 stp0 = vec2(1./ResS, 0. );vec2 st0p = vec2(0. , 1./ResT);vec2 stpp = vec2(1./ResS, 1./ResT);vec2 stpm = vec2(1./ResS, -1./ResT);float i00 = dot( texture2D( uImageUnit, vST ).rgb , LUMCOEFFS );float im1m1 = dot( texture2D( uImageUnit, vST-stpp ).rgb, LUMCOEFFS );float ip1p1 = dot( texture2D( uImageUnit, vST+stpp ).rgb, LUMCOEFFS );float im1p1 = dot( texture2D( uImageUnit, vST-stpm ).rgb, LUMCOEFFS );float ip1m1 = dot( texture2D( uImageUnit, vST+stpm).rgb, LUMCOEFFS );mjb – January 29, 2013Oregon State UniversityComputer Graphicsfloat ip1m1 = dot( texture2D( uImageUnit, vST+stpm).rgb, LUMCOEFFS );float im10 = dot( texture2D( uImageUnit, vST-stp0 ).rgb, LUMCOEFFS );float ip10 = dot( texture2D( uImageUnit, vST+stp0 ).rgb, LUMCOEFFS );float i0m1 = dot( texture2D( uImageUnit, vST-st0p ).rgb, LUMCOEFFS );float i0p1 = dot( texture2D( uImageUnit, vST+st0p ).rgb, LUMCOEFFS) );float h = -1.*im1p1 - 2.*i0p1 - 1.*ip1p1 + 1.*im1m1 + 2.*i0m1 + 1.*ip1m1;float v = -1.*im1m1 - 2.*im10 - 1.*im1p1 + 1.*ip1m1 + 2.*ip10 + 1.*ip1p1;float mag = sqrt( h*h + v*v );vec3 target = vec3( mag,mag,mag );color = vec4( mix( irgb, target, T ), 1. );Edge Detectionmjb – January 29, 2013Oregon State UniversityComputer GraphicsT = 0. T = 0.5 T = 1.float mag = sqrt( h*h + v*v );if( mag > uMagTol ){fFragColor= vec4( 0., 0., 0., 1. );}else{rgb.rgb *= uQuantize;Toon Renderingmjb – January 29, 2013Oregon State UniversityComputer Graphicsrgb.rgb *= uQuantize;rgb.rgb += vec3( .5, .5, .5 );ivec3 irgb = ivec3( rgb.rgb );rgb.rgb = vec3( irgb ) / uQuantize;fFragColor = vec4( rgb, 1. );}Toon RenderingOriginal ImageColors QuantizedOutlines Addedmjb – January 29, 2013Oregon State UniversityComputer GraphicsUse the GPU to enhance scientific, engineering, and architectural illustrationToon Rendering for