Qt 4.8: QGLColormap Class Reference

Qt Reference Documentation

# QGLColormap Class Reference

The QGLColormap class is used for installing custom colormaps into a QGLWidget. More...

     #include <QGLColormap>

- List of all members, including inherited members

## Public Functions

| QGLColormap ()
| QGLColormap ( const QGLColormap & map )
| ~QGLColormap ()
QColor | entryColor ( int idx ) const
QRgb | entryRgb ( int idx ) const
int | find ( QRgb color ) const
int | findNearest ( QRgb color ) const
bool | isEmpty () const
void | setEntries ( int count, const QRgb * colors, int base = 0 )
void | setEntry ( int idx, QRgb color )
void | setEntry ( int idx, const QColor & color )
int | size () const
QGLColormap & | operator= ( const QGLColormap & map )

## Detailed Description

The QGLColormap class is used for installing custom colormaps into a QGLWidget.

QGLColormap provides a platform independent way of specifying and installing indexed colormaps for a QGLWidget. QGLColormap is especially useful when using the OpenGL color-index mode.

Under X11 you must use an X server that supports either a `PseudoColor` or `DirectColor` visual class. If your X server currently only provides a `GrayScale`, `TrueColor`, `StaticColor` or `StaticGray` visual, you will not be able to allocate colorcells for writing. If this is the case, try setting your X server to 8 bit mode. It should then provide you with at least a `PseudoColor` visual. Note that you may experience colormap flashing if your X server is running in 8 bit mode.

The size() of the colormap is always set to 256 colors. Note that under Windows you can also install colormaps in child widgets.

This class uses implicit sharing as a memory and speed optimization.

Example of use:

     #include <QApplication>
     #include <QGLColormap>

     int main(int argc, char *argv[])
     {
         QApplication app(argc, argv);

         MySuperGLWidget widget;     // a QGLWidget in color-index mode
         QGLColormap colormap;

         // This will fill the colormap with colors ranging from
         // black to white.
         const int size = 256;
         for (int i = 0; i < size; ++i)
             colormap.setEntry(i, qRgb(i, i, i));

         widget.setColormap(colormap);
         widget.show();
         return app.exec();
     }

See also QGLWidget::setColormap() and QGLWidget::colormap().

## Member Function Documentation

### QGLColormap::QGLColormap ()

Construct a QGLColormap.

### QGLColormap::QGLColormap ( const QGLColormap & map )

Construct a shallow copy of map.

### QGLColormap::~QGLColormap ()

Dereferences the QGLColormap and deletes it if this was the last reference to it.

### QColor QGLColormap::entryColor ( int idx ) const

Returns the QRgb value in the colorcell with index idx.

### QRgb QGLColormap::entryRgb ( int idx ) const

Returns the QRgb value in the colorcell with index idx.

### int QGLColormap::find ( QRgb color ) const

Returns the index of the color color. If color is not in the map, -1 is returned.

### int QGLColormap::findNearest ( QRgb color ) const

Returns the index of the color that is the closest match to color color.

### bool QGLColormap::isEmpty () const

Returns true if the colormap is empty or it is not in use by a QGLWidget; otherwise returns false.

A colormap with no color values set is considered to be empty. For historical reasons, a colormap that has color values set but which is not in use by a QGLWidget is also considered empty.

Compare size() with zero to determine if the colormap is empty regardless of whether it is in use by a QGLWidget or not.

See also size().

### void QGLColormap::setEntries ( int count, const QRgb * colors, int base = 0 )

Set an array of cells in this colormap. count is the number of colors that should be set, colors is the array of colors, and base is the starting index. The first element in colors is set at base in the colormap.

### void QGLColormap::setEntry ( int idx, QRgb color )

Set cell at index idx in the colormap to color color.

### void QGLColormap::setEntry ( int idx, const QColor & color )

This is an overloaded function.

Set the cell with index idx in the colormap to color color.

### int QGLColormap::size () const

Returns the number of colorcells in the colormap.

### QGLColormap & QGLColormap::operator= ( const QGLColormap & map )

Assign a shallow copy of map to this QGLColormap.