rotate bmp (Xlib)

[Dariusz.Donimirski]

I must rotate bmp using Xlib without change bmp's memory. If someone
knows how I can do this, please help me.


dariusz
sorry about my english, I'm still learning

 

[Ben Pfaff]

I must rotate bmp using Xlib without change bmp's memory. If someone
knows how I can do this, please help me.

Perhaps you should ask about this in a newsgroup related to Xlib.
You are more likely to get correct responses if you ask there.

 

[Malcolm McLean]

I must rotate bmp using Xlib without change bmp's memory. If someone
knows how I can do this, please help me.

Load the bmp into memory.
I recently posted functions to do this.

Then apply the formula

ax = x - centralx;
ay = y - centraly;

(assuming you wnat to rotate about the centre)

theta is the angle to rotate by

bx = ax * cos(theta) - ay * sin(theta);
by = ax * sin(theta) + ay * cos(theta);

x = bx + centralx;
y = by + centraly;

Work from destination to source, or you will get missing pixel in the
destination image.
(For a very high quality rotate you need to do anti-alising as well).

Then you simply use Xlib to display the new image you have constructed. I'm
pretty sure it has no built-in rotate functions itself.