无法存储(保存)QPainter 图像
Can't Store(Save) the QPainter Image
我在 QPainter 的帮助下垂直组合了 2 个 QImage("firstImage" 和 "secondImage")。从屏幕截图可以看出,组合图像正确显示,没有错误:
Combined Image Displays Properly
但是如果我想使用 .save 存储 "combinedImage",程序会停止并且出现断言错误。
如何将合并后的图片存入硬盘?
mainwindow.cpp:
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QPainter>
#include <QImage>
#include <QPaintEvent>
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::paintEvent(QPaintEvent *)
{
QString firstImagePath = "/home/nvidia/Desktop/TestFolder/firstImage.jpg";
QString secondImagePath = "/home/nvidia/Desktop/TestFolder/secondImage.jpg";
QImage firstImage(firstImagePath);
QImage secondImage(secondImagePath);
QImage combinedImage;
QPainter paint(this);
paint.begin(&combinedImage);
paint.drawImage(0, 0, firstImage);
paint.drawImage(0, firstImage.height()*1.1, secondImage);
paint.end();
bool i = firstImage.save("/home/nvidia/Desktop/TestFolder/firstImage-Copy.bmp");
Q_ASSERT(i);
bool j = combinedImage.save("/home/nvidia/Desktop/TestFolder/combinedImage-Copy.bmp");
Q_ASSERT(j);
}
mainwindow.h:
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
void paintEvent(QPaintEvent *);
private:
Ui::MainWindow *ui;
};
#endif // MAINWINDOW_H
这是 Qt 输出:
Starting /home/nvidia/qtprojects/build-CombinedSave-Jetson_TX2-Debug/CombinedSave...
QPainter::begin: Painter already active
ASSERT: "j" in file ../CombinedSave/mainwindow.cpp, line 39
The program has unexpectedly finished.
/home/nvidia/qtprojects/build-CombinedSave-Jetson_TX2-Debug/CombinedSave crashed
firstImage-Copy.bmp 存储在 TestFolder 中,但 combinedImage-Copy.bmp 不是..
我的一些系统和程序属性:
ARMv8 Processor rev 3 (v8l) × 4 ARMv8 Processor rev 0 (v8l) × 2
Ubuntu 16.04 LTS
Qt Creator 3.5.1 Based on Qt 5.5.1 (GCC 5.2.1 20151129, 64 bit)
考虑代码...
QPainter paint(this);
paint.begin(&combinedImage);
第一行基本上是...
QPainter paint;
paint.begin(this);
并在 this
(您的 MainWindow
实例)上激活 QPainter
。但是你有...
paint.begin(&combinedImage);
在已经激活的 QPainter
上第二次调用 QPainter::begin
。这可能是错误消息的来源...
QPainter::begin: Painter already active
此外,您还使用默认 QImage
构造函数初始化 combinedImage
...
QImage combinedImage;
那时 combinedImage
是一个空图像 -- 它没有关联的大小或格式,不能按原样使用。
初始化和渲染combinedImage
尝试...
QImage combinedImage(std::max(firstImage.width(), secondImage.width()), /* Width */
firstImage.height() + secondImage.height(), /* Height */
QImage::Format_ARGB32_Premultiplied); /* Format */
{
QPainter paint(&combinedImage);
paint.drawImage(0, 0, firstImage);
paint.drawImage(0, firstImage.height(), secondImage);
}
我在 QPainter 的帮助下垂直组合了 2 个 QImage("firstImage" 和 "secondImage")。从屏幕截图可以看出,组合图像正确显示,没有错误:
Combined Image Displays Properly
但是如果我想使用 .save 存储 "combinedImage",程序会停止并且出现断言错误。
如何将合并后的图片存入硬盘?
mainwindow.cpp:
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QPainter>
#include <QImage>
#include <QPaintEvent>
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::paintEvent(QPaintEvent *)
{
QString firstImagePath = "/home/nvidia/Desktop/TestFolder/firstImage.jpg";
QString secondImagePath = "/home/nvidia/Desktop/TestFolder/secondImage.jpg";
QImage firstImage(firstImagePath);
QImage secondImage(secondImagePath);
QImage combinedImage;
QPainter paint(this);
paint.begin(&combinedImage);
paint.drawImage(0, 0, firstImage);
paint.drawImage(0, firstImage.height()*1.1, secondImage);
paint.end();
bool i = firstImage.save("/home/nvidia/Desktop/TestFolder/firstImage-Copy.bmp");
Q_ASSERT(i);
bool j = combinedImage.save("/home/nvidia/Desktop/TestFolder/combinedImage-Copy.bmp");
Q_ASSERT(j);
}
mainwindow.h:
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
void paintEvent(QPaintEvent *);
private:
Ui::MainWindow *ui;
};
#endif // MAINWINDOW_H
这是 Qt 输出:
Starting /home/nvidia/qtprojects/build-CombinedSave-Jetson_TX2-Debug/CombinedSave...
QPainter::begin: Painter already active
ASSERT: "j" in file ../CombinedSave/mainwindow.cpp, line 39
The program has unexpectedly finished.
/home/nvidia/qtprojects/build-CombinedSave-Jetson_TX2-Debug/CombinedSave crashed
firstImage-Copy.bmp 存储在 TestFolder 中,但 combinedImage-Copy.bmp 不是..
我的一些系统和程序属性:
ARMv8 Processor rev 3 (v8l) × 4 ARMv8 Processor rev 0 (v8l) × 2
Ubuntu 16.04 LTS
Qt Creator 3.5.1 Based on Qt 5.5.1 (GCC 5.2.1 20151129, 64 bit)
考虑代码...
QPainter paint(this);
paint.begin(&combinedImage);
第一行基本上是...
QPainter paint;
paint.begin(this);
并在 this
(您的 MainWindow
实例)上激活 QPainter
。但是你有...
paint.begin(&combinedImage);
在已经激活的 QPainter
上第二次调用 QPainter::begin
。这可能是错误消息的来源...
QPainter::begin: Painter already active
此外,您还使用默认 QImage
构造函数初始化 combinedImage
...
QImage combinedImage;
那时 combinedImage
是一个空图像 -- 它没有关联的大小或格式,不能按原样使用。
初始化和渲染combinedImage
尝试...
QImage combinedImage(std::max(firstImage.width(), secondImage.width()), /* Width */
firstImage.height() + secondImage.height(), /* Height */
QImage::Format_ARGB32_Premultiplied); /* Format */
{
QPainter paint(&combinedImage);
paint.drawImage(0, 0, firstImage);
paint.drawImage(0, firstImage.height(), secondImage);
}