What does it mean to convert photos of various sizes into centimeters and pixels?

The size of the photo is in inches, 1 inch =2.54cm, and usually x inches refers to the inch length of the long side of the photo. For example, 5 inches means that the photo length is 2.54x5 =12.7cm; 12 inch means that the length of the photo is 2.54x12 = 30.5cm. ..

ID card, physical examination form, etc. Most of them are 22×32mm small, 26mm×32mm second-generation ID cards, and 25mm×35mm ordinary one-inch photos. The standard photo size of passports and travel documents is 48mm×33mm, the head width is 2 1 mm ~ 24 mm, and the head length is 28 mm ~ 33 mm).

When the picture size is in pixels, we need to specify its fixed resolution in order to convert the picture size into the actual size in reality. For example, the resolution of the most commonly used pictures in web pages is 72, that is, 7265438 pixels per inch +0 inch equals 2.54 cm, then it can be concluded that each cm equals 28 pixels through conversion; Another example is a picture with the length of 15x 15cm, which is equal to the length of 420*420 pixels.

Extended data:

The expression of image resolution is also "horizontal pixel × vertical pixel", which can also be expressed by specification code.

But it should be noted that in different books, even in different places of the same book, the name of image resolution is different. In addition to the name image resolution, it can also be called image size, image size, pixel size and recording resolution.

Here, the two words "size" and "size" have double meanings, which can refer to both the number of pixels (quantity size) and the size of the picture (side length or area size), so it is easy to cause misunderstanding.

At the same display resolution, the higher the resolution, the more pixels and the larger the size and area of the image, so some people often use the image size and image size to represent the resolution of the image.

Baidu Encyclopedia-Image Resolution