how to load a Qt non-supported Image format

[Nithya]

I wated to load a 'tiff' image as a background image in the widget.

[jpn]

Which version of Qt are you using? As far as I remember, TIFF is supported since Qt 4.3. However, you will have to build the plugin if it's not already built. What does:

qDebug() << QImageReader::supportedImageFormats();

qDebug() << QImageReader::supportedImageFormats();

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output?

[Nithya]

I'm using Qt 4.2.2.And it doesnot support "tiff"
The list of supported formats are only
"bmp", "jpeg", "jpg", "mng", "pbm", "pgm", "png", "ppm", "svg", "xbm", "xpm".

[Nithya]

I am now trying with TiffIO plugin to load the Tiff.But I need a general solution to load any kind of non-supported format.Because I have to load dgn format and many other map formats to be loaded.

[jpn]

For unsupported formats you will need to provide an image format plugin.

[Vladd]

I am loading map image using GDAL library. Do this not by plugin. You can see this on https://sourceforge.net/projects/kmapexplorer, file gimgview.cpp function GImgLoader::loadTile.

Map are usually big and program load image block only when request come.

Here code:

pafScanline = (uchar *) CPLMalloc(xsize * ysize * 4);
    Q_CHECK_PTR(pafScanline);
    for (int i = 1; i <= 3; ++i) {  // R G B
        GDALRasterBand *poBand;
        poBand = m_dataset->GetRasterBand(i);
        Q_CHECK_PTR(poBand);
        static int smap[4] = { 0, 2, 1, 0 };
        if (poBand->RasterIO(GF_Read, x_off, y_off, xsize, ysize,
                             pafScanline + smap[i], xsize, ysize, GDT_Byte,
                             4, xsize * 4) == CE_Failure) {
            throw gException(QString("RasterIO error:%1").
                             arg(CPLGetLastErrorMsg()));
        }
    }
    QImage *result = new QImage(xsize, ysize, QImage::Format_RGB32);
    Q_CHECK_PTR(result);
    for (int y = 0; y < ysize; ++y) {
        QRgb *sLine = (QRgb *) result->scanLine(y);
        memcpy(sLine, pafScanline + y * xsize * 4, xsize * 4);
    }
    CPLFree(pafScanline);

pafScanline = (uchar *) CPLMalloc(xsize * ysize * 4);
    Q_CHECK_PTR(pafScanline);
    for (int i = 1; i <= 3; ++i) {  // R G B
        GDALRasterBand *poBand;
        poBand = m_dataset->GetRasterBand(i);
        Q_CHECK_PTR(poBand);
        static int smap[4] = { 0, 2, 1, 0 };
        if (poBand->RasterIO(GF_Read, x_off, y_off, xsize, ysize,
                             pafScanline + smap[i], xsize, ysize, GDT_Byte,
                             4, xsize * 4) == CE_Failure) {
            throw gException(QString("RasterIO error:%1").
                             arg(CPLGetLastErrorMsg()));
        }
    }
    QImage *result = new QImage(xsize, ysize, QImage::Format_RGB32);
    Q_CHECK_PTR(result);
    for (int y = 0; y < ysize; ++y) {
        QRgb *sLine = (QRgb *) result->scanLine(y);
        memcpy(sLine, pafScanline + y * xsize * 4, xsize * 4);
    }
    CPLFree(pafScanline);

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