iText

Question

我正在使用 iText 生成 PDF 文档，我想将渐变设置为页面背景。这可能吗？

Answer 1

（因为您只使用了标签 "itext"，没有使用 "itext7"，我假设您使用的是 iText 5.5.x。）

您可以使用 PdfShading 实例在 PdfContentByte canvas 上绘制轴向渐变：

PdfShading axial = PdfShading.simpleAxial(pdfWriter, x0, y0, x1, y1, startColor, endColor, extendStart, extendEnd);
canvas.paintShading(axial);

例如如果你想为现有PDF的所有页面添加浅红色到浅绿色的渐变，你可以这样做：

PdfReader pdfReader = new PdfReader(SOURCE);
PdfStamper pdfStamper = new PdfStamper(pdfReader, TARGET);
pdfStamper.setRotateContents(false);
for (int page = 1; page <= pdfReader.getNumberOfPages(); page++) {
    Rectangle pageSize = pdfReader.getPageSize(page);
    PdfShading axial = PdfShading.simpleAxial(pdfStamper.getWriter(),
            pageSize.getLeft(pageSize.getWidth()/10), pageSize.getBottom(),
            pageSize.getRight(pageSize.getWidth()/10), pageSize.getBottom(),
            new BaseColor(255, 200, 200), new BaseColor(200, 255, 200), true, true);
    PdfContentByte canvas = pdfStamper.getUnderContent(page);
    canvas.paintShading(axial);
}
pdfStamper.close();

(AddGradientBackground 测试 testStampGradientBackground)

或者，如果您想将浅红色到浅绿色渐变添加到您从头开始创建的 PDF 的所有页面，您可以这样做：

Document document = new Document();
PdfWriter pdfWriter = PdfWriter.getInstance(document, TARGET);
pdfWriter.setPageEvent(new GradientBackground());
document.open();
for (int i=0; i < 20; i++) {
    document.add(new Paragraph("Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet."));
}
document.close();

(AddGradientBackground 测试 testCreateWithGradientBackground)

使用这个助手class

class GradientBackground extends PdfPageEventHelper {
    @Override
    public void onEndPage(PdfWriter writer, Document document) {
        Rectangle pageSize = document.getPageSize();
        PdfShading axial = PdfShading.simpleAxial(writer,
                pageSize.getLeft(pageSize.getWidth()/10), pageSize.getBottom(),
                pageSize.getRight(pageSize.getWidth()/10), pageSize.getBottom(),
                new BaseColor(255, 200, 200), new BaseColor(200, 255, 200), true, true);
        PdfContentByte canvas = writer.getDirectContentUnder();
        canvas.paintShading(axial);
    }
}

(AddGradientBackground中的class)

结果如下所示：

iText - 如何将渐变设置为PDF文档的背景？

IText - How To Set Gradient As Background Of PDF Document?

java

pdf

document