Java iText缩放文档到A4 [英] Java iText scale document to A4

问题描述

我有以下方法可以调整大小":文档的所有页面均达到A4页面尺寸:

I have the following method that "resizes" all the pages of a document to A4 page dimensions:

  for (PdfDocument doc : pdfDocuments) {
        int n = doc.getNumberOfPages();
     
        for (int i = 1; i <= n; i++) {
         
            PdfPage page = doc.getPage(i);
        
            Rectangle media = page.getCropBox();
            if (media == null) {
                media = page.getMediaBox();
            }
          
            Rectangle crop = new Rectangle(0, 0, 210, 297);
            page.setMediaBox(crop);
            page.setCropBox(crop);

            // The content, placed on a content stream before, will be rendered before the other content
            // and, therefore, could be understood as a background (bottom "layer")
            new PdfCanvas(page.newContentStreamBefore(),
                    page.getResources(), doc).writeLiteral("\nq 0.5 0 0 0.5 0 0 cm\nq\n");

            // The content, placed on a content stream after, will be rendered after the other content
            // and, therefore, could be understood as a foreground (top "layer")
            new PdfCanvas(page.newContentStreamAfter(),
                    page.getResources(), doc).writeLiteral("\nQ\nQ\n");
        }
    }

但是，这不能按预期方式工作，页面被转换为A4(297x210)，但是内容没有放入内部(缩放)，内容被剪切，因为原始页面大于297X210.我该如何解决?

However , this is not working as expected , the pages are being transformed to A4 (297x210) BUT the content is not being fitted inside (scaled) , the content appears cutted because the original pages are larger than 297X210 . How can I fix this ?

推荐答案

在您澄清的评论中

我希望缩放先前内容的边界框，并在目标中添加边距

I want the bounding box of the former content be scaled and a margin be added in the target

因此，我们首先必须确定原始页面内容的边界框.可以使用 MarginFinder 类stackoverflow.com/a/56561952/1729265>此答案.当心:该类确定 all 内容的边界框，即使它只是一个白色矩形，在视觉上与其他内容或裁切框之外的内容也没有区别……如果您的用例需要，您可能还必须扩展该类，以考虑到这种情况.

So, we first have to determine the bounding box of the original page content. This can be done using the MarginFinder class from this answer. Beware: That class determines the bounding box of all content, even if it is merely a white rectangle visually not distinct from no content or something formerly outside the crop box... If your use case requires it, you may have to extend that class to take such circumstances into consideration, too.

确定了内容边界框后，剩下要做的就是一点计算.

With the content bounding box determined all that remains to do is a bit of calculation.

以下方法使用上面的类确定边界框，相应地转换内容，并更改结果裁剪框.

The following method determines the bounding box using the class above, transforms the content accordingly, and changes the result crop box.

void scale(PdfDocument pdfDocument, Rectangle pageSize, Rectangle pageBodySize) {
    int n = pdfDocument.getNumberOfPages();

    for (int i = 1; i <= n; i++) {
        PdfPage page = pdfDocument.getPage(i);

        MarginFinder marginFinder = new MarginFinder();
        PdfCanvasProcessor pdfCanvasProcessor = new PdfCanvasProcessor(marginFinder);
        pdfCanvasProcessor.processPageContent(page);
        Rectangle boundingBox = marginFinder.getBoundingBox();
        if (boundingBox == null || boundingBox.getWidth() == 0 || boundingBox.getHeight() == 0) {
            System.err.printf("Cannot scale page %d contents with bounding box %s\n", i , boundingBox);
            continue;
        } else {
            // Scale and move content into A4 with margin
            double scale = 0, xDiff= 0, yDiff = 0;
            double xScale = pageBodySize.getWidth()/boundingBox.getWidth();
            double yScale = pageBodySize.getHeight()/boundingBox.getHeight();
            if (xScale < yScale) {
                yDiff = boundingBox.getHeight() * (yScale / xScale - 1) / 2;
                scale = xScale;
            } else {
                xDiff = boundingBox.getWidth() * (xScale / yScale - 1) / 2;
                scale = yScale;
            }

            AffineTransform transform = AffineTransform.getTranslateInstance(pageBodySize.getLeft() + xDiff, pageBodySize.getBottom() + yDiff);
            transform.scale(scale, scale);
            transform.translate(-boundingBox.getLeft(), -boundingBox.getBottom());
            new PdfCanvas(page.newContentStreamBefore(), page.getResources(), pdfDocument)
                    .concatMatrix(transform);
        }
        page.setMediaBox(pageSize);
        page.setCropBox(pageSize);
    }
}

((对于A4结果页面尺寸，每边都有一英寸的空白，您可以这样称呼它作为PdfDocument pdfDocument:

For an A4 result page size with an inch of margin on each side you can call it like this for a PdfDocument pdfDocument:

Rectangle pageSize = PageSize.A4;
Rectangle pageBodySize = pageSize.clone().applyMargins(72, 72, 72, 72, false);
scale(pdfDocument, pageSize, pageBodySize);

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