compile error and where do you get the pixelWidth?

[alex-chan]

when compiled : ld: file not found: /Users/xxx/Library/Developer/Xcode/DerivedData/GPUImageFiltersDemo-bzyvxlxpdhpnehabsxyosuegkynk/Build/Products/Debug-iphoneos/GPUImageWaveFilterDemo.app/GPUImageWaveFilterDemo clang: error: linker command failed with exit code 1 (use -v to see invocation)

and where do you get uniform float texelWidth; uniform float texelHeight; It seems like they haven't been defined or passed in in GPUImageFilter