An open source graphical help tool library, fl_imgtk.

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Here is an open source library helps many Fl_RGB_Image processing to make some featured GUI.  You can clone or download source code in free on GitHub page.

It designed to work with any type of gcc ( llvm-gcc and MinGW-W64 ) with just a copy and type ‘make’, or modify Makefile.{your compiler} and copy to it as Makefile, then it could be compiled and writes libfl_imgtk.a into “lib” directory includes fl_imgtk.h.

What you can do ?

It provides some features to processing Fl_RGB_Image as like Photoshop.

  • Flip image in vertical or horizental.
  • Rotate image in any degree with smoothen pixels.
  • Adjusting contrast, bright and gamma.
  • Drawing image to blurred ( by using fl_smimg rescaling ).
  • Rescale with muliple filters ( nearest, bilinear, bicubic, lanczos, b-spline )
  • Tone mapping ( HDRi ) with two different algorithms : Drago and Reinhard ( refered to FreeImage3 )
  • Kernel matrix filtering ( basically supports blur, blur more, sharpen, sharpen more filters)
    Specially any user can make a new kernel filter easily.
  • Draw Fl_Widget to Fl_RGB_Image
  • Draw Fl_Widget to blurred Fl_RGB_Image as it could be used in cool background.
  • Cropping image to a part of new image.


Before you start with this open source library, prepare what FLTK library compiled or installed in your system. I amd working my clone version of FLTK 1.3.4-1.

First you need to do, download or cloen with your git into your working directoy. Then, copy Makefile.{your compiler} to Makefle. ( ex, cp Makefile.gcc Makefile )

Now just proceeding make.

If you faced to unknown reference of FLTK libraries, you may need edit Makefile.

You can changes FLTK_xxx configuration to your right place. It will works well any platform that availed to compile FLTK library.

Any question ?

You can make a new issue on my GitHub page, or my Guest book on my blog.



  • MIT License


External Licenses

  • FLTK license
  • FreeImage (3) license.