I am using Qt Designer 4.8.4 and I include two files in the QMainWindow resource file: a .ico file and a .gif file. When loading from code using:
QPixmap p;
*.ico is not supported.
By default, Qt supports the following formats:
Format Description Qt's support
BMP Windows Bitmap Read/write
GIF Graphic Interchange Format (optional) Read
JPG Joint Photographic Experts Group Read/write
JPEG Joint Photographic Experts Group Read/write
PNG Portable Network Graphics Read/write
PBM Portable Bitmap Read
PGM Portable Graymap Read
PPM Portable Pixmap Read/write
TIFF Tagged Image File Format Read/write
XBM X11 Bitmap Read/write
XPM X11 Pixmap Read/write