I am requested to provide an image file that should be supplied at 300 dpi resolution for .jpeg and .tiff or as .png files. I already have a png file here. When I check “file” in cmd I got:
Figure 1-1.png: PNG image, 560 x 747, 8-bit colormap, non-interlaced
From this information, how do I know that the file satisfies the requirement?
As I’ve previously said here and here…
PPI is not an inherent property of an image. There is no such thing as
a 300PPI image, or a 72PPI image. PPI is just a useful measurement for
determining the print size of an image.
Which means PPI is completely irrelevant unless accompanied by
physical dimensions. If someone says “Can we have that image in
300PPI?” they need to tell you a physical size in inches or
centimetrs or whatever else, otherwise the question makes no sense.
A 100 × 100 pixel image saved at 300 PPI is exactly the same as a
100 × 100 pixel image saved at 72 PPI, or 10 PPI, or 1 PPI. They are
even exactly the same if you print them at the same size.
The only times PPI is a useful measurement are…
You have a physical dimension requirement and you need to know how many pixels you need in your image.
Say you need a 6 × 4 inch image at 300 PPI, that allows you to
calculate how big in pixels your image needs to be. 6 × 4 (inches)
times 300 (PPI) is 1800 × 1200 — and there is your required size in
You have an image at a certain size in pixels, and you want to know how big you can print that image.
Say you have a 1800 × 1200 pixel image and you want to print it at
300 PPI. 1800 × 1200 (pixels) divided by 300 (PPI) is 6 × 4 — and that
is your print size in inches.
To directly answer the question…
Checking your file’s meta data won’t help.
You need to find the physical size requirements (in inches) and multiply those by 300 to get your pixel size requirements. If your image is that size (or bigger) then it is OK.
Source : Link , Question Author : TDT , Answer Author : Cai