QT 从ttf文件中读取图标
最近在做项目时，遇到需要显示一些特殊字符的需求，这些特殊字符无法从键盘敲出来，于是乎，发现可以从字体库文件ttf中读取显示。
参考博客：QT 图标字体类IconHelper封装支持Font Awesome 5-CSDN博客
该博客封装的很不错，值得一看！
一、下载ttf文件
Font Awesome，一套绝佳的图标字体库和CSS框架
解压出来后，通过如下网站可以在线查看键值对照关系
Iconfont Previewiconfont preview for web, Momo's Blog, LuckyMomo
https://blog.luckly-mjw.cn/tool-show/iconfont-preview/index.html很好玩的一个网站!
就可以看到该字体库解析出来的很多图标了。
这里请看图片中红色圆圈全中的 bug 图标，如果需要读取他，那么请记住他的编码：
注意，在代码中，我们用的是16进制方式，即：0xf188
在windows环境，右键字体，选择预览，即可看到字体名称！
字体名称 和 字体文件名 是必须要知道的！
二、编码
1.初始化字体后，就可以使用这个字体了
QFontDatabase::addApplicationFont("字体文件名"); // fontawesome-webfont.ttf
QFont iconFont = QFont("字体名称"); // FontAwesome2.从字体库中获取图标，返回QPixmap
QPixmap IconHelper::getPixmap(const QColor &color, const QChar &str,quint32 size, quint32 pixWidth, quint32 pixHeight, int flags)
{QPixmap pix(pixWidth, pixHeight);pix.fill(Qt::transparent);QPainter painter;painter.begin(&pix);painter.setRenderHints(QPainter::Antialiasing | QPainter::TextAntialiasing);painter.setPen(color);iconFont.setPixelSize(size);painter.setFont(iconFont);painter.drawText(pix.rect(), flags, str);painter.end();return pix;
}如果想要QImage，或者需要将图标保存为本地图片，则将QPixmap转为QImage后再保存本地即可。
IconHelper iconHelper("FontAwesome", "fontawesome-webfont.ttf");
QPixmap pixmap = iconHelper.getPixmap(QColor(0, 0, 0), QChar(0xf188), 300, 300, 300);
QImage iamge = pixmap.toImage(); // 转为 QImage
iamge.save("文件路径/文件名字.png"); // 保存为本地图片 
3.可以直接给部件设置背景图
void IconHelper::setIcon(QLabel *lab, const QChar &str, quint32 size)
{iconFont.setPixelSize(size);lab->setFont(iconFont);lab->setText(str);
}4.测试1，给按钮设置背景图标为篮球，图标编码为 0xf17d
int size = 100;
int width = 100;
int height = 100; IconHelper iconHelper("FontAwesome", "fontawesome-webfont.ttf");
QWidget *w = new QWidget;
w->setFixedSize(width*3, height*3); QPushButton *btn = new QPushButton(w);
btn->setFixedSize(width, height); iconHelper.setIcon(btn, QChar(0xf17d), size); QHBoxLayout *hLayout = new QHBoxLayout(w);
hLayout->addWidget(btn);
w->setLayout(hLayout); w->show(); 
5.测试2，给QLabel设置背景图标为虫子，图标编码为 0xf188
int size = 300;
int width = 300;
int height = 300; IconHelper iconHelper("FontAwesome", "fontawesome-webfont.ttf");
QPixmap p = iconHelper.getPixmap(QColor(0, 0, 0), QChar(0xf188), size, width, height); QWidget *w = new QWidget;
w->setFixedSize(p.size()); QLabel label(w);
label.setFixedSize(p.size());
label.setPixmap(p); QHBoxLayout *hLayout = new QHBoxLayout(w);
hLayout->addWidget(&label);
w->setLayout(hLayout); w->show(); 
三、代码汇总
iconhelper.h
#ifndef ICONHELPER_H
#define ICONHELPER_H#include <QtCore>
#include <QtGui>
#if (QT_VERSION > QT_VERSION_CHECK(5,0,0))#include <QtWidgets>
#endif//图形字体处理类
class IconHelper : public QObject
{Q_OBJECTpublic:explicit IconHelper(QString fontName, QString fontFileName, QObject *parent = nullptr);~IconHelper() override;void setIcon(QLabel *lab, const QChar &str, quint32 size = 12);void setIcon(QPushButton *btn, const QChar &str, quint32 size = 12);QPixmap getPixmap(const QColor &color, const QChar &str, quint32 size = 12,quint32 pixWidth = 15, quint32 pixHeight = 15, int flags = Qt::AlignCenter);private:QFont iconFont; // 图形字体
};
#endif // ICONHELPER_Hiconhelper.cpp
#include "iconhelper.h"IconHelper::IconHelper(QString fontName, QString fontFileName, QObject *parent) : QObject(parent)
{// 判断图形字体是否存在,不存在则加入QFontDatabase fontDb;if (!fontDb.families().contains(fontName)) {// 从资源文件中读取ttf文件int fontId = QFontDatabase::addApplicationFont(QString(":/image/%1").arg(fontFileName));QStringList fontName = QFontDatabase::applicationFontFamilies(fontId);if (0 == fontName.count()) {qDebug() << QString("load fontFileName error").arg(fontFileName);}}if (fontDb.families().contains(fontName)) {iconFont = QFont(fontName);
#if (QT_VERSION >= QT_VERSION_CHECK(4, 8, 0))iconFont.setHintingPreference(QFont::PreferNoHinting);
#endif} else { // 容错处理，如果字体加载失败，则使用默认字体QFont f;iconFont = f;}
}IconHelper::~IconHelper()
{}void IconHelper::setIcon(QLabel *lab, const QChar &str, quint32 size)
{iconFont.setPixelSize(size);lab->setFont(iconFont);lab->setText(str);
}void IconHelper::setIcon(QPushButton *btn, const QChar &str, quint32 size)
{iconFont.setPixelSize(size);btn->setFont(iconFont);btn->setText(str);
}QPixmap IconHelper::getPixmap(const QColor &color, const QChar &str,quint32 size, quint32 pixWidth, quint32 pixHeight, int flags)
{QPixmap pix(pixWidth, pixHeight);pix.fill(Qt::transparent);QPainter painter;painter.begin(&pix);painter.setRenderHints(QPainter::Antialiasing | QPainter::TextAntialiasing);painter.setPen(color);iconFont.setPixelSize(size);painter.setFont(iconFont);painter.drawText(pix.rect(), flags, str);painter.end();return pix;
}当根据大小获取到图标QPixmap后，就可以根据具体需要添加到相应的部件进行显示了！
完！