BMP display in QT c++

shashi prasad

Hi,

i am trying to display BMP in QT with below code. bmp downloaded correctly but image is not displayed.

fun(){

std::string szUrl("http://guest:p2guest@192.168.55.3/contents/2/icon/0874T2.bmp");
std::wstring wpathURL(szUrl.begin(), szUrl.end());
char *recByte = contmgr->Download(wpathURL.c_str());
QGraphicsScene scene;
QGraphicsView view(&scene);
QImage img;
img.fromData(recByte); // READING DATA
QPixmap pic;
pic.fromImage(img);
QGraphicsPixmapItem item(pic);
scene.addItem(&item);
view.show();

}

download function works fine, i have tested for other functionality.

please suggest me how to display bmp, what is issue with this code.

raven-worx

@shashi-prasad said in BMP display in QT c++:

QImage img;
img.fromData(recByte); // READING DATA
QPixmap pic;
pic.fromImage(img);

Not related to your issue, but there is no need to first create a QImage and then a QPixmap. You can create a QPixmap directly.

For your issue make sure have the imageplugins deployed/available.
What does the following return?

qDebug() << QImageReader ::supportedImageFormats()

J.Hilk

@shashi-prasad

QImage QImage::fromData(const uchar *data, int size, const char *format = Q_NULLPTR) is a static function that returns a QImage

QImage img;
img.fromData(recByte); // READING DATA

has no effect on img it will remain an null-image

try

QImage img = QImage::fromData(recByte);

shashi prasad

output of qDebug() << QImageReader ::supportedImageFormats(); is

("bmp", "cur", "dds", "gif", "icns", "ico", "jp2", "jpeg", "jpg", "pbm", "pgm", "png", "ppm", "svg", "svgz", "tga", "tif", "tiff", "wbmp", "webp", "xbm", "xpm")

output of qDebug()<<"recByte============="<<img.size(); is

recByte============= QSize(0, 0)

i think something wrong so it is showing 0,0.

i used as QImage img = QImage::fromData(recByte);

still output of qDebug()<<"recByte============="<<img.size(); is
recByte============= QSize(0, 0)

please suggest me.

J.Hilk

@shashi-prasad
my guess would be your recByte is empty or has an invalid header. You should check that.

Edit: Additional Info

if recByte is not empty check the 14 first Bytes.
0-1 => The header field used to identify the BMP
2-5 => Size of the BMP
6-9 => Reserved for the application that created the bmp file
10-14 => starting address, of the byte where the bitmap image data (pixel array) can be found.

SGaist

Hi,

Likely related to this thread.