JSPDF doesn't add images with online src

问题

In a web application I'm using JSPDF to convert the html to pdf. All works fine, except for the images. After a while, I noticed that it adds images that point to a local resource; instead, it does not add images that point to an online resource, and leaves in the place of the image an empty space, as if he expected it but could not load it.

For example: <img src="img/house.jpg"/> is correctly added. <img src="https://myurl.com/house.jpg"/> is not correctly added; there is an empty space instead of the image.

How can I solve it? Maybe store the image temporarily in local? I tried using addImage() but it is very hard to use, not only because I change the scale factor of pdf, but primarily because the content of the pdf is dynamic, and I do not know what size the images will have or their exact position.

回答1:

You need to make sure the image(s) is/are loaded before addIMage(). The following code is what I used to convert multiple images online to a PDF file. It will rotate the image(s) based on the orientation of the images/page and set proper margin. Note that this code is for image only, not html page with embedded image(s), but the concept of img.onload remains the same.

As for image rotation, if you see a blank page after rotation, it could simply be that the image is out of bounds. See this answer for details.

function exportPdf(urls) {
    let pdf = new jsPDF('l', 'mm', 'a4');
    const pageWidth = pdf.internal.pageSize.getWidth();
    const pageHeight = pdf.internal.pageSize.getHeight();
    const pageRatio = pageWidth / pageHeight;

    for (let i = 0; i < urls.length; i++) {
        let img = new Image();
        img.src = urls[i];
        img.onload = function () {
            const imgWidth = this.width;
            const imgHeight = this.height;
            const imgRatio = imgWidth / imgHeight;
            if (i > 0) { pdf.addPage(); }
            pdf.setPage(i + 1);
            if (imgRatio >= 1) {
                const wc = imgWidth / pageWidth;
                if (imgRatio >= pageRatio) {
                    pdf.addImage(img, 'JPEG', 0, (pageHeight - imgHeight / wc) / 2, pageWidth, imgHeight / wc, null, 'NONE');
                }
                else {
                    const pi = pageRatio / imgRatio;
                    pdf.addImage(img, 'JPEG', (pageWidth - pageWidth / pi) / 2, 0, pageWidth / pi, (imgHeight / pi) / wc, null, 'NONE');
                }
            }
            else {
                const wc = imgWidth / pageHeight;
                if (1 / imgRatio > pageRatio) {
                    const ip = (1 / imgRatio) / pageRatio;
                    const margin = (pageHeight - ((imgHeight / ip) / wc)) / 4;
                    pdf.addImage(img, 'JPEG', (pageWidth - (imgHeight / ip) / wc) / 2, -(((imgHeight / ip) / wc) + margin), pageHeight / ip, (imgHeight / ip) / wc, null, 'NONE', -90);
                }
                else {

                    pdf.addImage(img, 'JPEG', (pageWidth - imgHeight / wc) / 2, -(imgHeight / wc), pageHeight, imgHeight / wc, null, 'NONE', -90);
                }
            }
            if (i == urls.length - 1) {
                pdf.save('Photo.pdf');
            }
        }
    }
}

If this is a bit hard to follow, you can also use .addPage([imgWidth, imgHeight]), which is more straightforward. The downside of this method is that the first page is fixed by new jsPDF(). See this answer for details. You can use window.open(pdf.output('bloburl')) to debug.

来源：https://stackoverflow.com/questions/48126987/jspdf-doesnt-add-images-with-online-src