!rant

So nearly done with the work app and I need these images scaled accurately (it's for comparing pupils) my problem is I'd normally ask my brother to make the images but he is busy with uni for the next few weeks.

I'm just wondering is there a tool I can use that can rescale images (I have images from the iPhone app, and I gotta say I had to add in % changes despite the proper dpi sizing), I'm looking at the Android documentation but what's funny is in the listed resolutions OnePlus 3 wasn't included (along with some other newer resolutions) lol, and also Wikipedia for OnePlus 3 has the width and height switched (for some reason the author imagined the phone is also in landscape lol).

So do you guys know of something I can use? Programming is one thing but designer is another :/

I don't really understand what you want, but Irfanview has a batch image resizer and all that.

@620hun sorry I didn't explain it well,

So i have a bunch of images that need to be accurate to real dimensions (inches/millimetres).

Problem is my brother that can do this through Photoshop is currently busy with university projects.

The issue is that I have about 20 of these images for a specific phone size (or phone screen dimension, not sure of the correct term), I was just wondering if there was some sort of tool that exists to scale images on a large scale, that happens to work for Android screen dimensions (mdpi, hdpi, etc)

Also on the side note I'm not sure I completely understand dpi/ppi lol, since my phone (OnePlus 3) resolution is 1080x1920 and wiki states it's (401dpi) but display metrics says 420dpi.

Does my phone still come under the Android specific sizes (like hdpi, xhdpi, etc) or would I have to account for different sizes.

Hopefully that made more sense lol, but really confused as to this whole design thing.

Also I'll give irfanview a look thanks!

@f03n1x dpi/ppi = dots/pixels per inch.
It is based on the resolution and screen size. Here's an online tool to calculate dpi/ppi: https://www.sven.de/dpi/

I don't think you need to worry about the dpi value of the images.
A higher dpi image will look sharper and more crisp, but as long as you've set the ppi value to 200 or so, I don't think it will matter if some screens have 420 dpi and some have 250.
Besides, phone screens are quite small, and noticing a difference in clarity between an image with 200 ppi and one with 300 ppi is quite hard, even on a desktop monitor.

@JTBringe thanks for the info, but I figured out what dpi and ppi mean, though the issue is that the images have to be accurate sizes, the images are actually used to compare a person's pupils so they have to be correct measurements (9mm radius, 9.5mm radius, etc)

Well talked with my bro and I think in the end I'll just tell my boss that he has to get the company that does design work for the company to make them for particular phone sizes, it's just so much of a hassle dealing with the Android ranges, iPhone was too much of a pain (it has 3 x 20 images)