Is there a difference between 72dpi and 300dpi?

Question

Design

I am making a mobile application that creates a bitmap image (jpg) for printing on A4 with a resolution of 2480 × 3508px. The file properties state that dpi is 72.

To print A4 at 300dpi, you need a resolution of 2480 × 3508, which the application creates.

What will be the final dpi? is there any difference? the main thing is to stick to the resolution for 300dpi?

Answer 1

2480 × 3508px is not the resolution, but the dimensions of the image (in this case, in pixels).
dpi - the resolution with which a specific image is displayed on a specific device (on the screen - 72, on print (ideally) - 300). Depending on the ratio of dimensions (in pixels) and resolution, the image will have a specific size (in mm) on a specific device. For example, 2480/300 = 8.3 inches, 3508/300 = 11.7 inches, which is A4 paper size when printed at 300 dpi.
Open your image in Photoshop, look at its dimensions (Ctrl + Alt + I). Uncheck the Resample checkbox and try changing the dpi - only the physical dimensions in cm / mm will change, while the size in pixels will remain unchanged.
In other words, the pixel size of your image is sufficient for normal printing, because The printer will print at 300 resolution.

Answer 2

In the properties of the file it is written that dpi is 72.

These are metadata , the display of the file does not depend on them (any program can use them in any way or not use them at its discretion). At least 1 dpi will be indicated there, at least a million dpi. What matters is how many pixels are actually (2480 × 3508).