Swift - The resolution of the screen, the pixel of the picture, whether the pixel is a fixed size, the size of the screen, let's solve one by one

To Xiaobai:

1. Pixel: The attributes of the picture, we can see the screen on the bus scrolling to display the font. If you look closely, it is actually composed of LED lights. A pixel is an LED bulb, and a picture is actually many different colors. Composed of dots, this shop is pixel
2. Resolution: The property of the device screen. The resolution of iPhone6 ​​is 1334 x 750, which means that the iPhone has 750 pixels in the horizontal direction and 1334 pixels in the vertical direction.
3. Screen size: It is often said that the iPhone 6 is a 4.7-inch screen, and the XR is a 6.1-inch screen. The diagonal length of this screen is 4.7, 6.1 inches, and 1 inch equals 2.54cm.
4. Pixel size: As mentioned in 1 above, an LED bulb is a pixel, but some LED bulbs are small and some are large. The visible pixel size does not have a fixed size like 1 kg and 1 meter, and its size is relative

In summary of 1, 2, 3, 4, we can see that when the concept number comes, we should use the above data to understand something:

First of all, the horizontal and vertical pixel sizes are the same. All the pixels on a screen have the same size. For example, a 4.3-inch screen with a resolution of 1280x720 pixels, then its screen ratio is (16 : 9), through the Pythagorean theorem, you can calculate the length and width of 3.746X2.108 (95.2mmX53.5mm), 1280/3.746=341, that is, there are 341 pixels per inch, and each pixel has 95.2/1280= 0.074 mm large, 17-inch LCD display (5:4), its resolution: 1280X1024, 96 pixels per inch length; each side length is 0.263 mm

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