Merge pull request #2480 from swederik/fix/imageMapper-RGB-opacity

fix: Address incorrect opacity values when displaying RGB images in ImageMapper

Author: martinken

Sources/Rendering/OpenGL/ImageMapper/index.js

@@ -295,6 +295,18 @@ function vtkOpenGLImageMapper(publicAPI, model) {
             ]
           ).result;
           break;
+        case 3:
+          FSSource = vtkShaderProgram.substitute(
+            FSSource,
+            '//VTK::TCoord::Impl',
+            [
+              'vec4 tcolor = cscale0*texture2D(texture1, tcoordVCVSOutput.st) + cshift0;',
+              'gl_FragData[0] = vec4(texture2D(colorTexture1, vec2(tcolor.r,0.5)).r,',
+              '  texture2D(colorTexture1, vec2(tcolor.g,0.5)).r,',
+              '  texture2D(colorTexture1, vec2(tcolor.b,0.5)).r, opacity);',
+            ]
+          ).result;
+          break;
         default:
           FSSource = vtkShaderProgram.substitute(
             FSSource,