New method rgb2ColorIndex() to converts a 24-bit RGB color to a 256-color compatible approximation

ChangeLog

@@ -1,3 +1,7 @@
+2018-11-03  Markus Gans  <guru.mail@muenster.de>
+	* New method rgb2ColorIndex() to converts a 24-bit RGB color 
+	  to a 256-color compatible approximation
+
 2018-11-01  Markus Gans  <guru.mail@muenster.de>
 	* Moved FTerm debug access methods to FTermDebugData
 

README.md

@@ -12,7 +12,7 @@
      [![documented](https://codedocs.xyz/gansm/finalcut.svg)](https://codedocs.xyz/gansm/finalcut/hierarchy.html)
 
 The FINAL CUT is a C++ class library and widget toolkit with full mouse support for creating a [text-based user interface](https://en.wikipedia.org/wiki/Text-based_user_interface). The library supports the programmer to develop an application for the text console. It allows the simultaneous handling of multiple text windows on the screen.
-The C++ class design was inspired by the Qt framework. It provides common controls like dialog boxes, push buttons, check boxes, radio buttons, input lines, list boxes, status bars and so on.
+The structure of the Qt framework was originally the inspiration for the C++ class design of FINAL CUT. It provides common controls like dialog boxes, push buttons, check boxes, radio buttons, input lines, list boxes, status bars and so on.
 
 ### Installation
 ```bash

doc/faq.md

@@ -87,8 +87,8 @@ How can I fix display problems?
 * Make sure that the environment variable TERM has the right 
   terminal name.
 
-* With the command "`msgcat --color=test`" you can test whether 
+* Use the command "`msgcat --color=test`" to test whether the terminal 
-  the colors are displayed correctly in the terminal
+  displays colors correctly in the terminal.
 
 * If characters are not displayed in the right place on the screen, 
   it may help to disable cursor optimization for your program with 

doc/first-steps.md

@@ -72,7 +72,7 @@ The title bar of the dialog box gets the text "A dialog".
 dialog.setGeometry (25, 5, 30, 10);
 ```
 The dialog window gets a width of 30 and a height of 10 characters.
-The window in the terminal is located at the positions x=25 and
+The position of the window in the terminal is at x=25 and
 y=5 (note: x=1 and y=1 represents the upper left corner).
 
 ```cpp
@@ -93,7 +93,7 @@ if available) visible.
 return app.exec();
 ```
 The last line calls `exec()` to start the application and return
-the result to the operating system. When the application starts,
+the result to the operating system. The started application enters
-it enters the main event loop. This loop doesn't end until the
+the main event loop. This loop does not end until the window is
-window/application is closed.
+not closed.
 

src/fvterm.cpp

@@ -163,6 +163,20 @@ void FVTerm::setPrintCursor (int x, int y)
   }
 }
 
+//----------------------------------------------------------------------
+short FVTerm::rgb2ColorIndex (short r, short g, short b)
+{
+  // Converts a 24-bit RGB color to a 256-color compatible approximation
+
+  if ( r < 0 || g < 0 || b < 0 || r > 0xff || g > 0xff || b > 0xff )
+    return 0;
+
+  short ri = (((r * 5) + 127) / 255) * 36;
+  short gi = (((g * 5) + 127) / 255) * 6;
+  short bi = (((b * 5) + 127) / 255);
+  return 16 + ri + gi + bi;
+}
+
 //----------------------------------------------------------------------
 void FVTerm::clearArea (int fillchar)
 {

src/include/final/fvterm.h

@@ -153,6 +153,7 @@ class FVTerm
     void                  showCursor();
     void                  setPrintCursor (const FPoint&);
     void                  setPrintCursor (int, int);
+    short                 rgb2ColorIndex (short, short, short);
     void                  setColor (short, short);
     static void           setNormal();