Size of the images in iphone

Will the size of the (dimensions and also image storage siz开发者_StackOverflowe) change whensaving to iphone from our computer. I saved an image(1200x1600) of 100kB size to the iphone simulator via safari. From my application, i changes itsdimension to 640x480 and uploaded to server. But the uploaded image was of size 144KB!!! How does this happen??

Any image stored to the iPhone Photo albums on simulator or device will be 640x480. Images captured from the camera on 3GS in any case will 1200x1600 or there about. When you sync photos up to iPhone pictures are resized to 640x480 too. If you used a web service to get a picture there probably wouldn't be that restriction, but I haven't tried that.

The difference in size may be due to the picture format i.e. whether gif/jpg/png?