You can control whether images maintain their aspect during resizing using:
someImageInline.MaintainAspect = maintainImageAspect;
To loop through all images in a document you can use the following code:
NList<NNode> imageInlines = richText.Content.GetDescendants(NImageInline.NImageInlineSchema);
for (int i = 0; i < imageInlines.Count; i++)
((NImageInline)imageInlines[i]).MaintainAspect = true;
Let us know if you meet any problems or have any questions.
Nevron Support Team