ScanlineTextureMapperContext.cpp

// SPDX-License-Identifier: LGPL-2.1-or-later
//
// SPDX-FileCopyrightText: 2007 Carlos Licea <carlos _licea@hotmail.com>
// SPDX-FileCopyrightText: 2011 Bernhard Beschow <bbeschow@cs.tu-berlin.de>
//
 
#include "ScanlineTextureMapperContext.h"
 
#include "GeoSceneAbstractTileProjection.h"
#include "MarbleDebug.h"
#include "StackedTile.h"
#include "StackedTileLoader.h"
#include "TileId.h"
#include "ViewParams.h"
#include "ViewportParams.h"
 
using namespace Marble;
 
ScanlineTextureMapperContext::ScanlineTextureMapperContext(StackedTileLoader *const tileLoader, int tileLevel)
    : m_tileLoader(tileLoader)
    , m_textureProjection(tileLoader->tileProjection()->type())
    , // cache texture projection
    m_tileSize(tileLoader->tileSize())
    , // cache tile size
    m_tileLevel(tileLevel)
    , m_globalWidth(m_tileSize.width() * m_tileLoader->tileColumnCount(m_tileLevel))
    , m_globalHeight(m_tileSize.height() * m_tileLoader->tileRowCount(m_tileLevel))
    , m_normGlobalWidth(m_globalWidth / (2 * M_PI))
    , m_normGlobalHeight(m_globalHeight / M_PI)
    , m_tile(nullptr)
    , m_tilePosX(65535)
    , m_tilePosY(65535)
    , m_toTileCoordinatesLon(0.5 * m_globalWidth - m_tilePosX)
    , m_toTileCoordinatesLat(0.5 * m_globalHeight - m_tilePosY)
    , m_prevLat(0.0)
    , m_prevLon(0.0)
    , m_prevPixelX(0.0)
    , m_prevPixelY(0.0)
{
}
 
void ScanlineTextureMapperContext::pixelValueF(const qreal lon, const qreal lat, QRgb *const scanLine)
{
    // The same method using integers performs about 33% faster.
    // However we need the qreal version to create the high quality mode.
 
    // Convert the lon and lat coordinates of the position on the scanline
    // measured in radian to the pixel position of the requested
    // coordinate on the current tile.
 
    m_prevPixelX = rad2PixelX(lon);
    m_prevPixelY = rad2PixelY(lat);
 
    qreal posX = m_toTileCoordinatesLon + m_prevPixelX;
    qreal posY = m_toTileCoordinatesLat + m_prevPixelY;
 
    // Most of the time while moving along the scanLine we'll stay on the
    // same tile. However at the tile border we might "fall off". If that
    // happens we need to find out the next tile that needs to be loaded.
 
    if (posX >= (qreal)(m_tileSize.width()) || posX < 0.0 || posY >= (qreal)(m_tileSize.height()) || posY < 0.0) {
        nextTile(posX, posY);
    }
    if (m_tile) {
        *scanLine = m_tile->pixelF(posX, posY);
    } else {
        *scanLine = 0;
    }
 
    m_prevLon = lon;
    m_prevLat = lat; // preparing for interpolation
}
 
void ScanlineTextureMapperContext::pixelValue(const qreal lon, const qreal lat, QRgb *const scanLine)
{
    // The same method using integers performs about 33% faster.
    // However we need the qreal version to create the high quality mode.
 
    // Convert the lon and lat coordinates of the position on the scanline
    // measured in radian to the pixel position of the requested
    // coordinate on the current tile.
 
    m_prevPixelX = rad2PixelX(lon);
    m_prevPixelY = rad2PixelY(lat);
    int iPosX = (int)(m_toTileCoordinatesLon + m_prevPixelX);
    int iPosY = (int)(m_toTileCoordinatesLat + m_prevPixelY);
 
    // Most of the time while moving along the scanLine we'll stay on the
    // same tile. However at the tile border we might "fall off". If that
    // happens we need to find out the next tile that needs to be loaded.
 
    if (iPosX >= m_tileSize.width() || iPosX < 0 || iPosY >= m_tileSize.height() || iPosY < 0) {
        nextTile(iPosX, iPosY);
    }
 
    if (m_tile) {
        *scanLine = m_tile->pixel(iPosX, iPosY);
    } else {
        *scanLine = 0;
    }
 
    m_prevLon = lon;
    m_prevLat = lat; // preparing for interpolation
}
 
// This method interpolates color values for skipped pixels in a scanline.
//
// While moving along the scanline we don't move from pixel to pixel but
// leave out n pixels each time and calculate the exact position and
// color value for the new pixel. The pixel values in between get
// approximated through linear interpolation across the direct connecting
// line on the original tiles directly.
// This method will do by far most of the calculations for the
// texturemapping, so we move towards integer math to improve speed.
 
void ScanlineTextureMapperContext::pixelValueApproxF(const qreal lon, const qreal lat, QRgb *scanLine, const int n)
{
    // stepLon/Lat: Distance between two subsequent approximated positions
 
    qreal stepLat = lat - m_prevLat;
    qreal stepLon = lon - m_prevLon;
 
    // As long as the distance is smaller than 180 deg we can assume that
    // we didn't cross the dateline.
 
    const qreal nInverse = 1.0 / (qreal)(n);
 
    if (fabs(stepLon) < M_PI) {
        const qreal itStepLon = (rad2PixelX(lon) - m_prevPixelX) * nInverse;
        const qreal itStepLat = (rad2PixelY(lat) - m_prevPixelY) * nInverse;
 
        // To improve speed we unroll
        // AbstractScanlineTextureMapper::pixelValue(...) here and
        // calculate the performance critical issues via integers
 
        qreal itLon = m_prevPixelX + m_toTileCoordinatesLon;
        qreal itLat = m_prevPixelY + m_toTileCoordinatesLat;
 
        const int tileWidth = m_tileSize.width();
        const int tileHeight = m_tileSize.height();
 
        // int oldR = 0;
        // int oldG = 0;
        // int oldB = 0;
 
        QRgb oldRgb = qRgb(0, 0, 0);
 
        qreal oldPosX = -1;
        qreal oldPosY = 0;
 
        const bool alwaysCheckTileRange = isOutOfTileRangeF(itLon, itLat, itStepLon, itStepLat, n);
 
        for (int j = 1; j < n; ++j) {
            qreal posX = itLon + itStepLon * j;
            qreal posY = itLat + itStepLat * j;
            if (alwaysCheckTileRange)
                if (posX >= tileWidth || posX < 0.0 || posY >= tileHeight || posY < 0.0) {
                    nextTile(posX, posY);
                    itLon = m_prevPixelX + m_toTileCoordinatesLon;
                    itLat = m_prevPixelY + m_toTileCoordinatesLat;
                    posX = qBound<qreal>(0.0, (itLon + itStepLon * j), tileWidth - 1.0);
                    posY = qBound<qreal>(0.0, (itLat + itStepLat * j), tileHeight - 1.0);
                    oldPosX = -1;
                }
 
            *scanLine = m_tile->pixelF(posX, posY);
 
            // Just perform bilinear interpolation if there's a color change compared to the
            // last pixel that was evaluated. This speeds up things greatly for maps like OSM
            if (*scanLine != oldRgb) {
                if (oldPosX != -1) {
                    *(scanLine - 1) = m_tile->pixelF(oldPosX, oldPosY, *(scanLine - 1));
                    oldPosX = -1;
                }
                oldRgb = m_tile->pixelF(posX, posY, *scanLine);
                *scanLine = oldRgb;
            } else {
                oldPosX = posX;
                oldPosY = posY;
            }
 
            // if ( needsFilter( *scanLine, oldR, oldB, oldG  ) ) {
            //     *scanLine = m_tile->pixelF( posX, posY );
            // }
 
            ++scanLine;
        }
    }
 
    // For the case where we cross the dateline between (lon, lat) and
    // (prevlon, prevlat) we need a more sophisticated calculation.
    // However as this will happen rather rarely, we use
    // pixelValue(...) directly to make the code more readable.
 
    else {
        stepLon = (TWOPI - fabs(stepLon)) * nInverse;
        stepLat = stepLat * nInverse;
        // We need to distinguish two cases:
        // crossing the dateline from east to west ...
 
        if (m_prevLon < lon) {
            for (int j = 1; j < n; ++j) {
                m_prevLat += stepLat;
                m_prevLon -= stepLon;
                if (m_prevLon <= -M_PI)
                    m_prevLon += TWOPI;
                pixelValueF(m_prevLon, m_prevLat, scanLine);
                ++scanLine;
            }
        }
 
        // ... and vice versa: from west to east.
 
        else {
            qreal curStepLon = lon - n * stepLon;
 
            for (int j = 1; j < n; ++j) {
                m_prevLat += stepLat;
                curStepLon += stepLon;
                qreal evalLon = curStepLon;
                if (curStepLon <= -M_PI)
                    evalLon += TWOPI;
                pixelValueF(evalLon, m_prevLat, scanLine);
                ++scanLine;
            }
        }
    }
}
 
bool ScanlineTextureMapperContext::isOutOfTileRangeF(const qreal itLon, const qreal itLat, const qreal itStepLon, const qreal itStepLat, const int n) const
{
    const qreal minIPosX = itLon + itStepLon;
    const qreal minIPosY = itLat + itStepLat;
    const qreal maxIPosX = itLon + itStepLon * (n - 1);
    const qreal maxIPosY = itLat + itStepLat * (n - 1);
    return (maxIPosX >= m_tileSize.width() || maxIPosX < 0 || maxIPosY >= m_tileSize.height() || maxIPosY < 0 || minIPosX >= m_tileSize.width() || minIPosX < 0
            || minIPosY >= m_tileSize.height() || minIPosY < 0);
}
 
void ScanlineTextureMapperContext::pixelValueApprox(const qreal lon, const qreal lat, QRgb *scanLine, const int n)
{
    // stepLon/Lat: Distance between two subsequent approximated positions
 
    qreal stepLat = lat - m_prevLat;
    qreal stepLon = lon - m_prevLon;
 
    // As long as the distance is smaller than 180 deg we can assume that
    // we didn't cross the dateline.
 
    const qreal nInverse = 1.0 / (qreal)(n);
 
    if (fabs(stepLon) < M_PI) {
        const int itStepLon = (int)((rad2PixelX(lon) - m_prevPixelX) * nInverse * 128.0);
        const int itStepLat = (int)((rad2PixelY(lat) - m_prevPixelY) * nInverse * 128.0);
 
        // To improve speed we unroll
        // AbstractScanlineTextureMapper::pixelValue(...) here and
        // calculate the performance critical issues via integers
 
        int itLon = (int)((m_prevPixelX + m_toTileCoordinatesLon) * 128.0);
        int itLat = (int)((m_prevPixelY + m_toTileCoordinatesLat) * 128.0);
 
        const int tileWidth = m_tileSize.width();
        const int tileHeight = m_tileSize.height();
 
        const bool alwaysCheckTileRange = isOutOfTileRange(itLon, itLat, itStepLon, itStepLat, n);
 
        if (!alwaysCheckTileRange) {
            int iPosXf = itLon;
            int iPosYf = itLat;
            for (int j = 1; j < n; ++j) {
                iPosXf += itStepLon;
                iPosYf += itStepLat;
                *scanLine = m_tile->pixel(iPosXf >> 7, iPosYf >> 7);
                ++scanLine;
            }
        } else {
            for (int j = 1; j < n; ++j) {
                int iPosX = (itLon + itStepLon * j) >> 7;
                int iPosY = (itLat + itStepLat * j) >> 7;
 
                if (iPosX >= tileWidth || iPosX < 0 || iPosY >= tileHeight || iPosY < 0) {
                    nextTile(iPosX, iPosY);
                    itLon = (int)((m_prevPixelX + m_toTileCoordinatesLon) * 128.0);
                    itLat = (int)((m_prevPixelY + m_toTileCoordinatesLat) * 128.0);
                    iPosX = (itLon + itStepLon * j) >> 7;
                    iPosY = (itLat + itStepLat * j) >> 7;
                    // Bug 453332: Crash on Panning with Equirectangular Projection:
                    // https://bugs.kde.org/show_bug.cgi?id=453332
                    // Apparently at the edge of the latitude range a rounding error can move
                    // iPosY out of tile coords and nextTile will just reload the same tile.
                    // So let's just ensure that we stay in the expected range:
                    if (iPosY >= tileHeight)
                        iPosY = tileHeight - 1;
                    if (iPosY < 0)
                        iPosY = 0;
                }
 
                *scanLine = m_tile->pixel(iPosX, iPosY);
                ++scanLine;
            }
        }
    }
 
    // For the case where we cross the dateline between (lon, lat) and
    // (prevlon, prevlat) we need a more sophisticated calculation.
    // However as this will happen rather rarely, we use
    // pixelValue(...) directly to make the code more readable.
 
    else {
        stepLon = (TWOPI - fabs(stepLon)) * nInverse;
        stepLat = stepLat * nInverse;
        // We need to distinguish two cases:
        // crossing the dateline from east to west ...
 
        if (m_prevLon < lon) {
            for (int j = 1; j < n; ++j) {
                m_prevLat += stepLat;
                m_prevLon -= stepLon;
                if (m_prevLon <= -M_PI)
                    m_prevLon += TWOPI;
                pixelValue(m_prevLon, m_prevLat, scanLine);
                ++scanLine;
            }
        }
 
        // ... and vice versa: from west to east.
 
        else {
            qreal curStepLon = lon - n * stepLon;
 
            for (int j = 1; j < n; ++j) {
                m_prevLat += stepLat;
                curStepLon += stepLon;
                qreal evalLon = curStepLon;
                if (curStepLon <= -M_PI)
                    evalLon += TWOPI;
                pixelValue(evalLon, m_prevLat, scanLine);
                ++scanLine;
            }
        }
    }
}
 
bool ScanlineTextureMapperContext::isOutOfTileRange(const int itLon, const int itLat, const int itStepLon, const int itStepLat, const int n) const
{
    const int minIPosX = (itLon + itStepLon) >> 7;
    const int minIPosY = (itLat + itStepLat) >> 7;
    const int maxIPosX = (itLon + itStepLon * (n - 1)) >> 7;
    const int maxIPosY = (itLat + itStepLat * (n - 1)) >> 7;
    return (maxIPosX >= m_tileSize.width() || maxIPosX < 0 || maxIPosY >= m_tileSize.height() || maxIPosY < 0 || minIPosX >= m_tileSize.width() || minIPosX < 0
            || minIPosY >= m_tileSize.height() || minIPosY < 0);
}
 
int ScanlineTextureMapperContext::interpolationStep(const ViewportParams *viewport, MapQuality mapQuality)
{
    if (mapQuality == PrintQuality) {
        return 1; // Don't interpolate for print quality.
    }
 
    if (!viewport->mapCoversViewport()) {
        return 8;
    }
 
    // Find the optimal interpolation interval m_nBest for the
    // current image canvas width
    const int width = viewport->width();
 
    int nBest = 2;
    int nEvalMin = width - 1;
    for (int it = 1; it < 48; ++it) {
        int nEval = (width - 1) / it + (width - 1) % it;
        if (nEval < nEvalMin) {
            nEvalMin = nEval;
            nBest = it;
        }
    }
 
    return nBest;
}
 
QImage::Format ScanlineTextureMapperContext::optimalCanvasImageFormat(const ViewportParams *viewport)
{
    // If the globe covers fully the screen then we can use the faster
    // RGB32 as there are no translucent areas involved.
    QImage::Format imageFormat = (viewport->mapCoversViewport()) ? QImage::Format_RGB32 : QImage::Format_ARGB32_Premultiplied;
 
    return imageFormat;
}
 
void ScanlineTextureMapperContext::nextTile(int &posX, int &posY)
{
    // Move from tile coordinates to global texture coordinates
    // ( with origin in upper left corner, measured in pixel)
 
    int lon = posX + m_tilePosX;
    if (lon >= m_globalWidth)
        lon -= m_globalWidth;
    else if (lon < 0)
        lon += m_globalWidth;
 
    int lat = posY + m_tilePosY;
    if (lat >= m_globalHeight)
        lat -= m_globalHeight;
    else if (lat < 0)
        lat += m_globalHeight;
 
    // tileCol counts the tile columns left from the current tile.
    // tileRow counts the tile rows on the top from the current tile.
 
    const int tileCol = lon / m_tileSize.width();
    const int tileRow = lat / m_tileSize.height();
 
    m_tile = m_tileLoader->loadTile(TileId(0, m_tileLevel, tileCol, tileRow));
 
    // Update position variables:
    // m_tilePosX/Y stores the position of the tiles in
    // global texture coordinates
    // ( origin upper left, measured in pixels )
 
    m_tilePosX = tileCol * m_tileSize.width();
    m_toTileCoordinatesLon = (qreal)(0.5 * m_globalWidth - m_tilePosX);
    posX = lon - m_tilePosX;
 
    m_tilePosY = tileRow * m_tileSize.height();
    m_toTileCoordinatesLat = (qreal)(0.5 * m_globalHeight - m_tilePosY);
    posY = lat - m_tilePosY;
}
 
void ScanlineTextureMapperContext::nextTile(qreal &posX, qreal &posY)
{
    // Move from tile coordinates to global texture coordinates
    // ( with origin in upper left corner, measured in pixel)
 
    int lon = (int)(posX + m_tilePosX);
    if (lon >= m_globalWidth)
        lon -= m_globalWidth;
    else if (lon < 0)
        lon += m_globalWidth;
 
    int lat = (int)(posY + m_tilePosY);
    if (lat >= m_globalHeight)
        lat -= m_globalHeight;
    else if (lat < 0)
        lat += m_globalHeight;
 
    // tileCol counts the tile columns left from the current tile.
    // tileRow counts the tile rows on the top from the current tile.
 
    const int tileCol = lon / m_tileSize.width();
    const int tileRow = lat / m_tileSize.height();
 
    m_tile = m_tileLoader->loadTile(TileId(0, m_tileLevel, tileCol, tileRow));
 
    // Update position variables:
    // m_tilePosX/Y stores the position of the tiles in
    // global texture coordinates
    // ( origin upper left, measured in pixels )
 
    m_tilePosX = tileCol * m_tileSize.width();
    m_toTileCoordinatesLon = (qreal)(0.5 * m_globalWidth - m_tilePosX);
    posX = lon - m_tilePosX;
 
    m_tilePosY = tileRow * m_tileSize.height();
    m_toTileCoordinatesLat = (qreal)(0.5 * m_globalHeight - m_tilePosY);
    posY = lat - m_tilePosY;
}