Chrome扩展程序屏幕截图用于Retina显示屏的部分图像裁剪 [英] Chrome extension screenshot partial image cropping for Retina Display

问题描述

我做了一个chrome扩展程序，它捕获了网站的单个元素(div).

I made a chrome extension, which captures a single element (div) of a website.

我使用chrome.tabs> captureVisibleTab制作了屏幕截图.然后，使用元素(div)的坐标(x/y)和大小(width/height)裁剪屏幕截图.

I used chrome.tabs > captureVisibleTab to make a screenshot. Then, with the coordinates (x/y) and sizes (width/height) of the element (div) I crop the screenshot.

在非视网膜显示器上，这对我来说效果很好.但是在配备Retina显示屏的Macbook上却不是.

This works fine for me on non-retina displays. But not so on a Macbook with Retina display.

例如，在www.247activemedia.com上，我们希望捕获带有徽标(id ="header")的标头div.

For example, on www.247activemedia.com, we want to capture the header div with the logo (id="header").

在非视网膜上的结果是:

On non-retina result is:

在具有Retina显示屏的Macbook上:

On a Macbook with Retina display:

那里的裁剪失败，并且结果也不正确.

Cropping failed there, and also the resultion is not correct.

这是代码:

chrome.tabs.captureVisibleTab(tab.windowId, { format: "png" }, function(screenshot) {
            if (!canvas) {
                canvas = document.createElement("canvas");
                document.body.appendChild(canvas);
            }
            var partialImage = new Image();
            partialImage.onload = function() {
                canvas.width = dimensions.width;
                canvas.height = dimensions.height;
                var context = canvas.getContext("2d");
                context.drawImage(
                    partialImage,
                    dimensions.left,
                    dimensions.top,
                    dimensions.width,
                    dimensions.height,
                    0,
                    0,
                    dimensions.width,
                    dimensions.height
                );
                var croppedDataUrl = canvas.toDataURL("image/png");
                chrome.tabs.create({
                    url: croppedDataUrl,
                    windowId: tab.windowId
                });
            }
            partialImage.src = screenshot;

        });

如何为Retina显示器解决此问题?

How can I fix this for Retina Displays?

推荐答案

好吧，感谢@ gui47-答案是使用 window.devicePixelRatio 检测缩放，该缩放在我的MBP上返回2

Ok, thanks to @gui47 -- the answer is to detect scale with window.devicePixelRatio which is returning 2 on my MBP

这篇关于Chrome扩展程序屏幕截图用于Retina显示屏的部分图像裁剪的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！