QImage创建清空和空判断

QImage(1280,720,QImage::Format_RGBA8888); //宽度以4对齐
QImage img("1.jpg");
if(!img.load("1.jpg")){}
QImage img(data,1280,720,QImage::Format_RGBA8888) //uchar *data
QImage img = src.copy();
QImage img(src);
img = QImage(); //清空
img.isNull();
img.save("1.png");

QImage数据读写

QColor pixelColor(int x,int y) const;
uchar *scanLine(int i);
uchar *bits();
void setPixelColor(int x,int y,const QColor *color)
void fill(const QColor &color)
int bytesPerLine() const;
int byteCount() const;

QImage存储图片

bool save(const QString &fileName,const char* format = Q_NULLPTR,int quality = -1);
quality 0-100
format 0表示根据文件名

QImage图像的缩放

QImage QImage::scaled(const QSize &size, Qt::AspectRatioMode aspectRatioMode = Qt::IgnoreAspectRatioMode = Qt::IgnoreAspectRatio,Qt::TransformationMode,transformMode = Qt::FastTransformation) const;

widget.cpp

#include "widget.h"
#include "ui_widget.h"
#include <QPainter>Widget::Widget(QWidget *parent): QWidget(parent), ui(new Ui::Widget)
{ui->setupUi(this);img = QImage(1280,720,QImage::Format_RGBA8888);img.fill(QColor(255,0,0,200));  //遍历设置颜色uchar *data = img.bits();//假定已对齐 不对齐就出错for(int i = 0; i < img.width();i++){for(int j = 0; j < img.height() / 2;j++){data[j*img.width()*4 + i * 4] = 0; //Rdata[j*img.width()*4 + i * 4+1] = 255; //G data[j*img.width()*4 + i * 4+1] = 0; //Bdata[j*img.width()*4 + i * 4+1] = 255; //A}}for(int i = img.width()/2; i < img.width();i++){for(int j = 0; j < img.height() / 2;j++){img.setPixelColor(i,j,QColor(0,0,0,255));}}}void Widget::paintEvent(QPaintEvent *ev)
{QPainter p(this);if(!img.isNull()){p.drawImage(0,0,img);   }
}Widget::~Widget()
{delete ui;
}