A brief talk on Web Mobile terminal basic

Screen size, screen resolution, screen pixel density

屏幕尺寸：           指屏幕的对角线的长度，单位是英寸，1英寸=2.54厘米。                常见的屏幕尺寸有2.4、2.8、3.5、3.7、4.2、5.0、5.5、6.0等。屏幕分辨率：（iphone6  750*1334）        指在横纵向上的像素点数，单位是px，1px=1个像素点。一般以纵向像素*横向像素来表示一个手机的分辨率，                如1960*1080。（这里的1像素指的是物理设备的1个像素点）屏幕像素密度/像素密度/屏幕密度：        屏幕上每英寸可以显示的像素点的数量，单位是ppi，即“pixels per inch”的缩写。        屏幕像素密度与屏幕尺寸和屏幕分辨率有关

Physical pixels, CSS pixels

 Device pixel/physical pixel: (resolution) When you buy a phone, you have a resolution of N x M, which is the n x m image point of the screen, and a point (Wangfang) is a physical pixel.            It is the smallest granularity the screen can display.                 Device pixels, also known as physical pixels, are the smallest physical part of a display device.            Each pixel can set its own color and brightness based on the operating system.            The number of physical pixels for any device is a fixed CSS pixel: css pixels are an abstract unit that is used primarily on the browser to accurately measure (determine) the content on a Web page.            It is created for web developers, an abstract layer used in CSS or JavaScript in general, CSS pixels are called device-independent pixels (device-independent pixels), referred to as "DIPs". At a standard display density (normal screen), a CSS pixel corresponds to a device pixel.            The relationship between CSS pixels and physical pixels a width of 200px element, which occupies 200 css pixels, but 200 css pixels occupy how many physical pixels depends on the characteristics of the screen (whether it is high density, that is, pixel ratio) and the user's scaling behavior. On Apple's Retina screen, the retina's pixel density is twice times that of a normal screen, which spans 400 device pixels. If the user zooms in, it will span more devices pixel device independent pixels: device independent pixels (also called density independent pixels), can be considered a computer coordinate system in a Point, which represents a virtual pixel (such as a CSS pixel) that can be used by a program, and then converted by the relevant system to physical pixels. Bit image element: A bitmap pixel is a raster image (such as PNG, JPG, GIF, etc.) the smallest data unit 1 bit pixels corresponding to 1 physical pixel, the picture can get a perfect and clear display for Web developers: every CSS we use and JavaScript-defined pixels essentially represent CSS pixels, and we don't care about how many device pixels a CSS pixel crosses in the development process. We will rely on the screen features andTo the browser for a complex calculation of the user's zoom level. 

Pixel ratio

像素比:它的官方的定义为：设备物理像素和设备独立像素的比例，        也就是 devicePixelRatio = 物理像素 /独立像素            window.devicePixelRatio

A brief talk on Web Mobile terminal basic