ScanlineTextureMapperContext.h

// SPDX-License-Identifier: LGPL-2.1-or-later
//
// SPDX-FileCopyrightText: 2007 Andrew Manson <g.real.ate@gmail.com>
// SPDX-FileCopyrightText: 2011 Bernhard Beschow <bbeschow@cs.tu-berlin.de>
//
 
#ifndef MARBLE_SCANLINETEXTUREMAPPERCONTEXT_H
#define MARBLE_SCANLINETEXTUREMAPPERCONTEXT_H
 
#include <QSize>
#include <QImage>
 
#include "GeoSceneTileDataset.h"
#include "MarbleMath.h"
#include "MathHelper.h"
 
namespace Marble
{
 
class StackedTile;
class StackedTileLoader;
class ViewportParams;
 
 
class ScanlineTextureMapperContext
{
public:
    ScanlineTextureMapperContext( StackedTileLoader * const tileLoader, int tileLevel );
 
    void pixelValueF( const qreal lon, const qreal lat,
                      QRgb* const scanLine );
    void pixelValue( const qreal lon, const qreal lat,
                     QRgb* const scanLine );
 
    void pixelValueApproxF( const qreal lon, const qreal lat,
                            QRgb *scanLine, const int n );
    void pixelValueApprox( const qreal lon, const qreal lat,
                           QRgb *scanLine, const int n );
 
    static int interpolationStep( const ViewportParams *viewport, MapQuality mapQuality );
 
    static QImage::Format optimalCanvasImageFormat( const ViewportParams *viewport );
 
    int globalWidth() const;
    int globalHeight() const;
 
private:
    // method for fast integer calculation
    void nextTile( int& posx, int& posy );
 
    // method for precise interpolation
    void nextTile( qreal& posx, qreal& posy );
 
    // Converts Radian to global texture coordinates 
    // ( with origin in center, measured in pixel) 
    qreal rad2PixelX( const qreal lon ) const;
    qreal rad2PixelY( const qreal lat ) const;
 
    // Checks whether the pixelValueApprox method will make use of more than
    // one tile
    bool isOutOfTileRange( const int itLon, const int itLat,
                           const int itStepLon, const int itStepLat,
                           const int n ) const;
 
    bool isOutOfTileRangeF( const qreal itLon, const qreal itLat,
                            const qreal itStepLon, const qreal itStepLat,
                            const int n ) const;
 
private:
    StackedTileLoader *const m_tileLoader;
    GeoSceneAbstractTileProjection::Type const m_textureProjection;
    /// size of the tiles of the current texture layer
    QSize const m_tileSize;
 
    int const        m_tileLevel;
    int const        m_globalWidth;
    int const        m_globalHeight;
    qreal const      m_normGlobalWidth;
    qreal const      m_normGlobalHeight;
 
    const StackedTile *m_tile;
 
    // Coordinate transformations:
 
    // Position of the tile in global Texture Coordinates
    // ( with origin in upper left corner, measured in pixel) 
    int          m_tilePosX;
    int          m_tilePosY;
 
    // Converts global texture coordinates 
    // ( with origin in center, measured in pixel) 
    // to tile coordinates ( measured in pixel )
    qreal  m_toTileCoordinatesLon;
    qreal  m_toTileCoordinatesLat;
 
    // Previous coordinates
    qreal  m_prevLat;
    qreal  m_prevLon;
    qreal  m_prevPixelX;
    qreal  m_prevPixelY;
};
 
inline int ScanlineTextureMapperContext::globalWidth() const
{
    return m_globalWidth;
}
 
inline int ScanlineTextureMapperContext::globalHeight() const
{
    return m_globalHeight;
}
 
inline qreal ScanlineTextureMapperContext::rad2PixelX( const qreal lon ) const
{
    return lon * m_normGlobalWidth;
}
 
inline qreal ScanlineTextureMapperContext::rad2PixelY( const qreal lat ) const
{
    switch ( m_textureProjection ) {
    case GeoSceneAbstractTileProjection::Equirectangular:
        return -lat * m_normGlobalHeight;
    case GeoSceneAbstractTileProjection::Mercator:
        if ( fabs( lat ) < 1.4835 ) {
            // We develop the inverse Gudermannian into a MacLaurin Series:
            // In spite of the many elements needed to get decent 
            // accuracy this is still faster by far than calculating the 
            // trigonometric expression:
            // return - asinh( tan( lat ) ) * 0.5 * m_normGlobalHeight;
 
            // We are using the Horner Scheme as a polynom representation
 
            return - gdInv( lat ) * 0.5 * m_normGlobalHeight;
        }
        if ( lat >= +1.4835 )
            // asinh( tan (1.4835)) => 3.1309587
            return - 3.1309587 * 0.5 * m_normGlobalHeight; 
        if ( lat <= -1.4835 )
            // asinh( tan( -1.4835 )) => −3.1309587
            return 3.1309587 * 0.5 * m_normGlobalHeight; 
    }
 
    // Dummy value to avoid a warning.
    return 0.0;
}
 
}
 
#endif