Pixel calculation

Hello:
to calculate the number of pixels in an image, you need to:
divide the length of the image by inches (2.54), multiply that by the DPI (dots per inch), and multiply all of that by the width divided by inches multiplied by the DPI.
For example: length of an image: 10 cm
width of the image: 15 cm
DPI: 72
(10/2.54*72)*(15/2.54*72)= 12528911 pixels

To calculate the number of pixels in an image, you first need to know the length and width of the image.
One square inch equals 2.54 square centimeters, which is equivalent to 6.45 square centimeters. Thus,
exercise
let’s consider an RGB color image with a resolution of 70 ppi, where the length of this image is 15 cm and its width is 10 cm.
1. Calculate the number of pixels in this image?
Therefore, we have 1 square inch = (2.54)^2 = 6.45 square centimeters.
Number of pixels = 15 * 10 = 150 square centimeters.
1 square inch = 6.45 square centimeters.
1 square inch corresponds to 70 * 70 pixels.
Square inch = 150 / 6.45 = 23.25 square inches.
Number of pixels = ?.............. 23.25 square inches.
70 * 70 corresponds to 1 square inch.
Number of pixels = 70 * 70 * 23.25 / 1 = 113925 pixels.

Hello,
Please help me crop an image from 800/600 to 600/600
In short, I would like to be able to use Photofiltre or GIMP to get an image 600/600 as the American lottery requires!!
When I type 600/600, it immediately gives me an image of 450/600 instead... I'm done for, please!

simple yet ..... easy trick...
Imagine a cube in front view, 500 pixels by 500 pixels on three layers Red, Green, and Blue (note that CMYK = 4 layers, for printing).
In terms of depth, to describe the colors you have 8 bits per layer or 16 bits per layer (common values but not exclusive).
This depth determines the quality of your chromatics but has no effect on your definition or the sharpness of your image.
I don't know your processing software but make images by testing the number of bits.
For example, we use 2 bits per layer for Black/white, 8 bits per layer for shades of gray, etc...
On your scanner, you always use the maximum bit depth to capture the maximum nuances of colors.
In desktop publishing graphics, you have good books on color processing, definitions, basics, and practical aspects generally under Photoshop but also on layout software (InDesign, QuarkXPress) and vector drawing (Illustrator) etc.... Photography books are generally less comprehensive.
Also, consider how you use this information... professional?... informed amateur? very informed.... passerby between two chocolates.....