Quote:
Originally Posted by lilman
Dpi is the density of pixels in an image.
|
I understand what DPI is but I just don't understand why we need to worry about it. If I'm making a wallpaper for my PC or a smartphone, all I care about is the resolution (ie: 1280x1024, 480x320)... I don't need to worry about the PC being 72dpi and the Smartphone being 200dpi. But if someone gave me an image and said that it was scanned at 1200dpi and I need to print it at 1200dpi to match the original, then I can set my printer to that dpi. Reader devices have a fixed display dpi so there is no way we can match the original. I bet if the output was a bitmap instead of PDF, you wouldn't need to worry about it either. But alas, I don't believe PDF allows for a pixel as a unit of measurement, and thus you are probably forced to use DPI. This is probably why manga/comics are packaged in a cbz/cbr instead of PDF... since there is no way to force a PDF to display an image with 1:1 pixel correctness and without interpolation. Ok, I think we are off topic now.
Quote:
Originally Posted by lilman
Using % with images is tricky because of dpi. This is made even more tricky since I think there are some images that you can't determine the dpi of (very annoying problem, it's the reason I use ImageMagick to determine dpi instead of letting Java handle it).
|
I used percentage because specifying a pixel amount doesn't make sense. For example, 100 pixels for a 1600x1200 page is small, but huge for a 800x600 page. With percentage, you calculate the number of pixels relative to the resolution of the page: ie: width pixels = width resolution x %, height pixels = height resolution x %. Unless your input file is PDF, you are still working with non-physical bitmaps and thus DPI is unimportant until the very end when you need to output to PDF. Some image formats like jpeg allow for metadata to be included, such as dpi, but I have never needed to worry about it... I can only imagine it being relevant if I wanted to print it to paper and don't want different image elements to look different. One day, we may have screens that match the dpi of print... when that day comes, then we probably no longer need to worry about resolution and just care about dpi.
Good luck on your new project. We certainly don't want you to get burned out doing the same thing... but please revisit!