QT 如何将数据导出成PDF文件（QPdfWriter 使用指南）

在平时使用一些文字编辑软件时，我们可能经常会遇到“输出为PDF”，那究竟是如何做到的呢？本文将使用QPdfWriter + QPainter，实现把 QGradient::Preset 对应的颜色效果图，导出为PDF文件。以下是示例代码：

1、示例代码

QString pdfName = "QGradientPreset";
pdfName.append(QDateTime::currentDateTime().toString("yyyyMMdd-HHmmss"));
pdfName.append(".pdf");
QString filePath = QFileDialog::getSaveFileName(this, QStringLiteral("导出QGradient预设值"), pdfName, "*.pdf");
if (filePath.isEmpty()) {
    
	return;
}

//
QFile pdfFile(filePath);
if (!pdfFile.open(QIODevice::WriteOnly)) {
    
	return;
}
QPdfWriter* pdfWriter = new QPdfWriter(&pdfFile);
//初始化QPdfWriter
pdfWriter->setPageSize(QPagedPaintDevice::A4);
pdfWriter->setResolution(300); //设置dpi(一般是96)
pdfWriter->setPageMargins(QMargins(30, 30, 30, 30));

//绘制PDF内容
QPainter* painter = new QPainter(pdfWriter);
painter->setRenderHint(QPainter::Antialiasing);
int pdfWidth = painter->viewport().width();
int pdfHeight = painter->viewport().height();

int colorIndex = 0;
int posTop = 0;
int posLeft = 0;
int width = 530;//色块宽度
int height = 180;//色块高度
int margin = 20;//色块间距

//绘制标题文字
painter->setFont(QFont("NSimSun", 20, QFont::Normal));
painter->drawText(QRect(posLeft, posTop, pdfWidth, height),
	Qt::AlignCenter,
	QString::fromLocal8Bit("QGradient Preset 色值对照图"));

//色块的起始纵坐标
posTop += height;

//paint begin
while (colorIndex < 180)//QGradient::Preset::NumPresets - 1
{
    
	colorIndex++;
	//
	QGradient::Preset clr = QGradient::Preset(colorIndex);
	painter->fillRect(QRect(posLeft, posTop, width, height), clr);
	//
	painter->setFont(QFont("NSimSun", 14, QFont::Normal));
	painter->drawText(QRect(posLeft, posTop, width, height),
		Qt::AlignCenter, 
		QString::fromLocal8Bit("Preset: %1").arg(colorIndex));

	posLeft += (width + margin);
	int posRight = posLeft + width;
	if (posRight >= pdfWidth)
	{
    
		posLeft = 0;
		//
		posTop += (height + margin);
		int posButtom = posTop + height;
		if (posButtom >= pdfHeight)
		{
    
			pdfWriter->newPage();
			posTop = 0;
		}
	}
}
//paint end

//delete it
delete painter;
delete pdfWriter;
pdfFile.close();

//
QDesktopServices::openUrl(QUrl::fromLocalFile(filePath));

2、输出的pdf文件内容

3、其他

Qt助手提供的网页链接：https://webgradients.com/
另：代码中所需要的包含的头文件，请自行添加。