Creating images from png

BlitzMax Forums/BlitzMax Programming/Creating images from png

Robert Cummings

(Posted 2006) [#1]

Hi,

I have a really long png file which I would like to operate on and cut out images. I will be loading this file as a pixmap (for various reasons).

The images will be drawn using DrawImage and use the alpha channel contained within the png file.

Ideally I would like to make several images from this file, of varying sizes at runtime. Could you please assist me in this task?

Thanks!

GfK	(Posted 2006) [#2]

This is how I'm currently doing it. I guess you can just load the image as a pixmap if you want, and dispense with the LockImage stuff.

image.tImage = LoadImage("myImage.png")
frame:tImage = LoadImage(PixmapWindow(LockImage(image),x,y,width,height))

Robert Cummings

(Posted 2006) [#3]

This causes my game to crash for some reason at drawimage. Not quite sure why.

Robert Cummings

(Posted 2006) [#4]

I have to warn you against this method. It created scrambled graphics on my card with really long source images. I tried both loadpixmap and loadimage as source.

Another issue: images don't always get "loaded". You need to pretty much draw straight away on some cards?

GfK	(Posted 2006) [#5]

Possibly a problem with non-square pixmaps then?

Robert Cummings

(Posted 2006) [#6]

which is bizarre, because pixmaps are ok non-squared. Hmmm.... I have it working but on this card I *have* to draw it immediately as I grab it into an image or the image is lost (becomes null) and crashes if I try to draw it later.

GfK	(Posted 2006) [#7]

Are you nulling the original pixmap after PixmapWindow? I'm fairly sure you have to leave the original there, as PixmapWindow just creates a pointer to an existing area of memory - once the pixmap is nulled/cleaned up by GC you'll get problems.