Apply a functor to each pixel in an Image

afw supports for_each_pixel as a way to process each pixel in an Image, in a similar way to the STL's for_each. The name doesn't follow the LSST C++ guidelines, but in this case I felt that conformity to the spirit of the STL was more important. There are variants of for_each_pixel corresponding to setting a pixel to a function, setting it to a function of an Image, and setting it to a function of its value and a second Image's pixel value. The selection of which of these operations is desired is done by requiring the functor to inherit from a class such as pixelOp0 or pixelOp1XY, each of which is a std::function with a virtual operator() added.

for_each_pixel(Image<LhsT> &lhs, pixelOp0<LhsT> const& func)

Set each pixel in lhs to the value of func.

for_each_pixel(Image<LhsT> &lhs, pixelOp1<LhsT> const& func)

Set each pixel in lhs to the value of func(lhs).

for_each_pixel(Image<LhsT> &lhs, pixelOp1XY<LhsT> const& func)

Set each pixel in lhs to the value of func(x, y, lhs).

for_each_pixel(Image<LhsT> &lhs, Image<RhsT> const& rhs, pixelOp1<RhsT> const& func)

Set each pixel in lhs to the value of func(lhs).

for_each_pixel(Image<LhsT> &lhs, Image<RhsT> const& rhs, pixelOp2<Lhs, RhsT> const& func)

Set each pixel in lhs to the value of func(lhs, rhs).

for_each_pixel(Image<LhsT> &lhs, Image<RhsT> const& rhs, pixelOp2XY<Lhs, RhsT> const& func)

Set each pixel in lhs to the value of func(x, y, lhs, rhs).

Example of using for_each_pixel

This code is in . forEachPixel.cc ImageAlgorithm.h namespace Include needed header file, and define a namespace alias }; Here's the simplest possible functor, simply setting each pixel to 0. Note that operator() is declared const, as we pass these functors by (const reference. If this surprises you, take a look at Meyers, Effective STL, Item 38. }; This one's a bit more interesting. We save a value in the constructor, and use it to set each pixel. It's analogous to std::fill but if I called it fill then following a using namespace std; the compiler would complain about ambiguity; it's simpler just to use a different name. }; }; Here are examples of pixelOp1 and pixelOp2 }; A functor designed to add a Gaussian to an image img2 Declare a couple of Images to play with cout cout cout cout Apply erase to each pixel in img1 setVal to each pixel in img2 set img1 = img2 + 1, and finally img1 /= img1 cout Add a Gaussian to the image, centered at (xc, yc) and with central intensity 1000. }