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 <QImage>
#include <QSize>
 
#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