I was allready successfull to resize pictures to place them with the right relations in a picturebox (I have to present 16 pictures - just like thumbnails - on a form; the original imagesizes can go up to 6 MB).
Problem: it takes too much time.

My procedure:
Load picture in SpecialPicturebox
Estimate the Height and Width
If Height>Width then Calculate scalingfactor1 else Calculate scalingfactor2
load picture in Picturebox1 with proper scalingfactor

(Imagebox with autostreching gives deformed pictures!)

Remark:
Previewing 16 pictures in my solution can take 10 sec, previewing them in Windows explorer will take only 0,1 sec (estimate).
Who has a faster solution?