Скачать или смотреть How to Set Element Size in Real Pixels

Discover how to ensure that your web elements, such as images and divs, maintain a consistent size across devices by using CSS and javascript methods. Learn to ignore device pixels and set fixed pixel size with simple solutions.
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How to Set Element Size in Real Pixels

In the world of web design, ensuring that your elements appear in the correct size on various devices can be a challenging task. A common scenario arises when you want to capture a screenshot of a specific element, such as an iframe or a div, but notice that its dimensions are not what you expected—especially on high-resolution screens. In this guide, we'll dive into a specific problem related to CSS sizing and provide you with an effective solution to ensure that your elements maintain their intended size in real pixels.

The Problem

Imagine you are generating a screenshot of a webpage that is displayed in an iframe, and you want that screenshot to be strictly 100x100 pixels. While this functionality works well on lower resolution screens, on high-resolution displays, the downloaded image may appear at larger dimensions (e.g., 200x200 pixels). This discrepancy happens because the device pixel density changes the way dimensions are interpreted.

In a nutshell, you want to ignore device pixels and force your screenshots and elements to appear as true pixels. How do you achieve that?

The Solution

The good news is that there is a straightforward solution to this problem using the html2canvas library in JavaScript. By applying a modification to your existing code, you can enforce the element size to be rendered in real pixels. Follow this guide to implement the changes effectively.

Step-by-step Guide

Set Up Your HTML and CSS: Start with defining your HTML structure, ensuring that you have a div with specific dimensions set in pixels.

[[See Video to Reveal this Text or Code Snippet]]

Modify Your Screenshot Logic: When calling html2canvas, incorporate the scale parameter to ensure it captures the element with the desired pixel dimensions.

[[See Video to Reveal this Text or Code Snippet]]

Explanation of the Code

html2canvas Function: This function takes a DOM element as a parameter and generates a canvas image based on that element's layout and style.

{ scale: 1 }: This critical setting tells html2canvas to maintain the actual pixel size of the element as defined in the CSS, ignoring the device pixel ratio. This is especially important for high-resolution screens where each CSS pixel may correspond to multiple device pixels.

Blob Creation and Download: The code converts the rendered canvas to a downloadable blob image that can be saved locally.

Conclusion

By implementing the adjustment to the html2canvas function with the scale parameter, you get precise control over how your screenshots appear, ensuring they align with the designated pixel dimensions across varying device resolutions. This approach will help maintain consistency in your design, ultimately enhancing the user experience.

Key Takeaways

Use the scale: 1 property with the html2canvas for accurate pixel sizes.

Ensure that your CSS dimensions are set in pixels for better control.

Test your implementation across different devices to verify consistency.

Now, you can confidently capture elements in true pixels without the worry of them being distorted on high-resolution displays!