Image Resize for web

[guitarzan8]

How do I convert the resolution of a jpg image from 150 dpi to 72 dpi? I do not want the image size (width/height) to change. I tried to Scale Image, but when I change the resolution, the width and height changes. WHen I change the width and height, the resolution changes.

 

[moldboy]

Let's think of it this way:
We shall pretend that the file image is 4px by 8px and 2dpi (for easy numbers) this would then make the image, when printed, 2 inches by 4 inches, understand? Because that is what dpi refers to, when you place an image on the internet the dpi really doesn't mean anything (to my understanding) because a monitor has a DPI predefined so to speak, we call it resolution. Many people are confused by this, they ask how many pixles in an inch, well that would depend on the dpi, that is the same for a picture, you can open a 600X400 pixle image on a computer screen and measure it, the size of the image will change according to the number of dots currently represented on the screen so if your resolution is 640X 480 the image will represent most of the screen, but if the screen is set to 1024X768 well then the once good looking picture will be very small. So in the quality of an image there are three factors, pixles, inches (cm, mm, picas) and dpi, you can't just change one without affecting atleast one of the other. By changing the DPI the actual pixle count of the image must change for the size to stay the same, if the size stays the same and you increase to pixcle count then the DPI will increase.

I can see by the date of your post that this probably won't help you, but maybe others.

 

[guitarzan8]

Yes, I've used XP Paint since then as well as XP jpg resize tool. and yes, I think you are right, it won't help me. The question still seeks an answer though.

 

[TonyGroves]

Select Image -> Scale Image.
Divide the Width figure by 150/72, and change the X and Y resolution to 72 pixels/inch.