An open source graphical help tool library, fl_imgtk.

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.

Fixing SD card unexpected unmounting problem of Oukitel U20 plus SIM tray.

Oukitel U20 plus was a good budget smartphone has FHD resolution and dual cameras priced under 100 USD in the world from China.

But some people may have experience about “Unexpected SD card unmounted” problem in real life. All apps turned to gray and it doesn’t run while SD card mounted again by hitting back side of SIM tray again.

So I have to fix this prblem, and tear off back cover with some stripping tools.

Now I understand why U20 plus so heavy, and astonished Oukitel grown up well to architecting better than before about times of K6000. Some lacks by mistery of price under 100 USD, may acceptable – inside back cover color was white, I was expected black or dark inside.

Examined why SD card going unmounted in unexpected times, and found reason of this.

It was seems to reason of cost reduction, low cost componet problem of SIM tray + SD card. There’s nothing like shielding metal covers on component, just rare plastic itself made weakage on bending inside by pressure. Here I explained why it going worst:

To prevent unexpected unmounting SD card by any shock, I need put shomething to make depth to same beside EMI shielded block of right side. I put couple of transparency urethane film, and it made depth more thicker. And it made for better than befoe, test many shock by hitting area of SIM tray and it not happened to unmounting SD card again.

It may better put something to make fill gap between back cover and SIM tray component, and it may not considered on designing step or, lack of reason to cost reduction to make it more cheaper by Oukitel.

Hope make it better by reading my article who anybody looking for solution to fix this problem as like me.