How Can I Accurately Detect System DPI/PPI Using JavaScript and CSS?

Detecting System DPI/PPI: JavaScript and CSS to the Rescue

To cater to varying screen resolutions, detecting the system's DPI or PPI (pixels per inch) is crucial for generating images tailored to specific devices. However, initial explorations suggest that this may be a challenge.

Initial Approaches:

• Using the CSS property "1in" to determine the offsetWidth encounters limitations on some devices (e.g., iPhone).
• Estimating DPI/PPI by calculating the display's dimensions and pixel width, but no explicit implementation details are available.

A Solution with JavaScript and CSS:

To address these challenges, the following approach leverages JavaScript and CSS to accurately detect system DPI/PPI:

<div>

How it Works:

1. Creating a Hidden Element with Unit Size: An invisible HTML element with a specified height of 1 inch is created and hidden using CSS.
2. Device Pixel Ratio: The devicePixelRatio is retrieved. This value represents the ratio of physical pixels to CSS pixels.
3. DPI/PPI Calculation: The element's offsetWidth and offsetHeight are multiplied by the devicePixelRatio to calculate the device's DPI or PPI in the X and Y axes.
4. Result Display: The computed DPI or PPI values are logged to the console.

The above is the detailed content of How Can I Accurately Detect System DPI/PPI Using JavaScript and CSS?. For more information, please follow other related articles on the PHP Chinese website!