Posts by CarmenZ

    Dear Zhuomuke,

    a convulution of an image with a filter in the frequency domain can be performed via multiplication.

    In the VisualApplets design "FFtandbandpass.va" this is done correctly. After the image is transformed via FFT to frequency space a multiplication with a filter image (buffered in operator CoefficientBuffer) is performed. The filter image ( e.g. bandpass filter) buffered in the operator Coefficient Buffer can be generated using external software.

    Dear Zhuomuke,

    thank you for your question. The meaning "Foward" as value of Parameter "Transformation Mode" of the operator "FFT" means transformation to frequency space. With value "Inverse" the FFT operator transforms the frequency space to "normal"image space. The functionality of FFT operator in this mode corresponds to Inverse Fast Fourier Transform. To transform an image with no imaginary part to frequency space set the lower (imaginary ) input node of operator "FFT" to constant value "Zero". In your VisualApplets installation directory under Examples/processing/Advanced/FastFourierTransform you can find an example implementation.

    In the design snippet in the attachment a way to buffer a sequence of 3 images and output them simulataneously is implemented. With simple modifications the example can be modified for other image sequence lengths. To process images of a sequence simultaneously is e.g. important for High Dynamic Range Imaging or Exposure Fusion.

    Please see also the Visual Applets example implementations (in the installation directory) for High Dynamic Range Imaging and Exposure Fusion to see the usage of the image sequence operation.

    Hi,

    in the VisualApplets design "AddDummies.va" a simple way to create dummy pixel for empty images is introduced. For some image operations like Blob analysis or thresholding with subsequent pixel removement empty images might occur. Using operator "IsLastPixel" you have the possibility to simply create dummy pixels for this case. Please find more informations in the commentboxes in the design.

    Files

    • AddDummies.va

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