PureBasic Forums - English

I'm still very much a PB beginner but getting a bit better with practice.

I want to simplify the 24 bit RGB data in a colour bitmap into a 'custom' 8-bit format (imagine it's a grayscale, although that's not exactly what I'll be doing). Assume the original image is a .jpg. I then want to do a bit of threshold detection math on the custom data. Finally, I want to show a (rudimentary) thumbnail image using the custom data,

My solution:

Using the .jpg converter plug-in, load the image.
Save the loaded image as a .bmp
Open the .bmp as a 'binary' file (do we have those in PB?)
Read the first part of the file, ie the .bmp header- get file length, image height/width etc
DIM array.l() as a store for the 8-bit data
Read sequentially the R+G+B data from the .bmp file
Do the 24 to 8 bit math conversion and store result in array()
Do the 'analysis' stuff on array() & save to disk
Read through array(), then use a palette to return some 'pseudoRGB' values
Display the pseudoRGB using PLOT

I've tried the PLOT routine by simply drawing on a window. I don't have a particular speed problem with that. I expect it could display faster using StartDrawing(ImageOutput)/ImageGadget/LoadImage or better still, drawn onto a WindowedScreen. That's not a priority.

This seems very kludgy. Can I access the actual image data in memory using PEEK? What are the other better ways?

Thanks.

Al

Change the image's colour depth. Here's some code.

You can use the API's GetObject_(), GetDIBits_(), and some others if you're on Windows. Here's a thread that deals somewhat in the areas you want to touch, with some usage examples:

http://www.purebasic.fr/english/viewtopic.php?t=35627

This might actually be a good feature request, I was fooling around with storing images in databases (in Yenc actually) and found it annoying I couldn't seem to find some statement to retrieve them from or create them in memory...

isn't the Image a standard Image object?
and isn't the handle returned by ImageID(#) an OS-handle to the Image object?
and doesn't the Object header contain a pointer to the Image matrix?

... and aren't there tons of API functions ... netmaestro already said this one ..