Can Qt Convert jpg images to the BMP format?

redstoneleo

Can Qt Convert jpg images to the BMP format? If possible ,please give a little code,thanks .

tried

QImage('C:\\0dbcaadd144059fd76c6388a.jpg').save('C:\\2.jpg',"BMP")

but just return False, anyone know why ?

Googled, but not find an answer .

raven-worx

QPixmap pix("path-to/image.jpg");
pix.save("path-to/image.bmp");

Also see this

SGaist

Hi,

Something like:

QImage myJpgImage("path_to_jpeg.jpg");
qDebug() << myJpgImage.save("path_to_bitmap.bmp");

?

More information in the QImage documentation here and here

[edit: it's been a long time since synchronous posting raven-worx :D]

redstoneleo

tried
@
QImage('C:\0dbcaadd144059fd76c6388a.jpg').save('C:\2.jpg',"BMP")
@
but just return False, anyone know why ?
[quote author="SGaist" date="1421848773"]Hi,

Something like:

@
QImage myJpgImage("path_to_jpeg.jpg");
qDebug() << myJpgImage.save("path_to_bitmap.bmp");
@

?

More information in the QImage documentation "here":http://doc.qt.io/qt-5/qimage.html#reading-and-writing-image-files and "here":http://doc.qt.io/qt-5/qimage.html#save

[edit: it's been a long time since synchronous posting raven-worx :D][/quote]

redstoneleo

Have you tried it ? save() just return false
[quote author="raven-worx" date="1421848703"]@
QPixmap pix("path-to/image.jpg");
pix.save("path-to/image.bmp");
@

Also see "this":http://doc.qt.io/qt-5/qtimageformats-index.html[/quote]

raven-worx

[quote author="SGaist" date="1421848773"]
[edit: it's been a long time since synchronous posting raven-worx :D]
[/quote]
yep! i was quite busy the last year :)

[quote author="redstoneleo" date="1421850868"]Have you tried it ? save() just return false[/quote]
more than once, yes :)

ok lets try something else then. What does the following return?
@
QImageWriter::supportedImageFormats();
@
If the list contains "BMP" you should check if you are allowed to read/write the image files from/to the path you've specified.

Also you should avoid something like this:
@
QImage('C:\0dbcaadd144059fd76c6388a.jpg').save('C:\2.jpg',"BMP")
@
Qt automatically checks the file extension and chooses the right "codec" to write the image.

Edit: I am also not quite sure if it is allowed to write to "C:" in all cases (e.g. when you don't run the application as Administrator for example)

SGaist

To add to raven-worx, the file extension is the first thing checked, if Qt doesn't find a corresponding encoder, it's use the second parameter as a hint.

Also, you can use unix's forward slash notation with Qt, so you don't take the risk of messing your path because you forgot a double backslash.

redstoneleo

The reason why it didn't work before is I changed the image's suffix from jpg to bmp subjectively,then use QImage::save() to convert format to bmp, thus it faild, after correct this mistake ,it worked now!

BTW,for
@bool QImage::save(const QString & fileName, const char * format = 0, int quality = -1) const@
If format is 0, QImage will attempt to guess the format by looking at fileName's suffix,so format is prior to fileName's suffix.