PNG-format application icon renders badly

[Alex Taylor]

It's common to use an image (e.g. from Qt resources) of an internally-supported format such as PNG for the frame icon. Indeed, this seems to be the only way to be able to access the image in other contexts within the application (see ticket #305).

Unfortunately, it renders very badly in this case, with ugly scaling and broken alpha-blending.

In theory, it should be possible to avoid scaling by providing an icon of the exact size. For example:

QIcon icon;
icon.addFile(":/images/editor.png", QSize( 40, 40 ), QIcon::Normal, QIcon::On );
icon.addFile(":/images/editor_mini.png", QSize( 20, 20 ), QIcon::Normal, QIcon::On );
icon.addFile(":/images/editor_vga.png", QSize( 32, 32 ), QIcon::Normal, QIcon::On );
icon.addFile(":/images/editor_vga_mini.png", QSize( 16, 16 ), QIcon::Normal, QIcon::On );
setWindowIcon( icon );

This works (and looks) fine when rendering the image in an explicit context inside the program, such as via MessageBox::about().

However, when used as the application icon, either the wrong image size is being selected, or it's being re-scaled somehow (why or to what, I cannot tell).

Screenshots to be attached.

[Alex Taylor]

Correct rendering of 20x20 and 40x40 PNG images (in about box).

[Alex Taylor]

Ugly rendering of PNG image as application icon.

[Alex Taylor]

Ugly rendering of PNG image as application mini-icon (in system menu).

[Alex Taylor]

The first screenshot shows what the 40x40 and 20x20 PNG images actually look like. Here they are rendered (via MessageBox::about()) as they should be.

The second and third screenshots show how the exact same (QIcon) images are rendered as the application full-size and mini-icon, respectively. As can be seen, they look terrible.

[Silvan Scherrer]

Ticket retargeted after milestone closed

[Silvan Scherrer]

please test with Qt 5 and open a ticket at ​https://github.com/bitwiseworks/qtbase-os2 if it's not good enough.