GTKMM::在GTk::绘图区域使用单个Gdk::PixBuf绘制多个图像

Question

大家好，我试图在Gtk::DrawingArea中绘制实时图像，就像它们在火车站，机场，地铁等显示器上显示的那样。

为了当前测试的目的，我已经硬编码了我的代码。

在这里

Gtk::绘图区域宽度=720，高度=640。我是第一个。PGM和第二。PGM图像每个有360*640的尺寸。(是的，我为了测试的目的旋转了它。)这些图像每像素包含一个字节。

1)绘制单幅图像时绘制精细。我刚刚读取图像到unsigned char* buffer大小为360*640*3。我是这样读的

int bufferIndex=0; 
int fileIndex=0; //just assume 
for (int i=0; i<height; i++)
{
     for (int j=0; j<width; j++)
     {
         //below three lines are for RGB purpose required in Gdk::Pixbuf
         buffer[bufferIndex++] = //File[fileIndex]; 
         buffer[bufferIndex++] = //File[fileIndex]; 
         buffer[bufferIndex++] = //File[fileIndex]; 
     }
}               
Gdk::Colorspace colorSpace = Gdk::COLORSPACE_RGB;
Gdk::Colorspace colorSpace = (Gdk::Colorspace)0;
bool has_alpha = false;
int bits_per_sample = 8;
int rowStride = 360*3; // distance between rows in bytes
Glib::RefPtr<Gdk::Pixbuf> pixBuf = Gdk::Pixbuf::create_from_data((const guint8 *) buffer,
       colorSpace, has_alpha, bits_per_sample, 360, 640, rowStride);
Glib::RefPtr<Gdk::GC> gcContext;
pixBuf->render_to_drawable(drawingArea pointer, gcContext, 0, 0, 0 , 0 , 360, 640, Gdk::RGB_DITHER_MAX, 0, 0);
//It prints the image in the left half of drawing area. 

这是一样的，我的预期，但有一个问题，当我试图画两个图像。为此，我先读书。PGM在缓冲区，之后我读第二。PGM(表示总[360*640*3]*2字节)现在我按照代码所示绘制它。

Glib::RefPtr<Gdk::GC>gcContext;
Gdk::Colorspace colorSpace = Gdk::COLORSPACE_RGB;
Gdk::Colorspace colorSpace = (Gdk::Colorspace)0;
bool has_alpha = false;
int bits_per_sample = 8;
int rowStride = 360*3; // distance between rows in bytes
Glib::RefPtr<Gdk::Pixbuf> pixBuf = Gdk::Pixbuf::create_from_data((const guint8 *) buffer,
       colorSpace, has_alpha, bits_per_sample, 720, 640, rowStride);
pixBuf->render_to_drawable(drawingarea pointer, gcContext, 0, 0, 0 , 0 , 720, 640, Gdk::RGB_DITHER_MAX, 0, 0);

在两半中，首先。PGM打印

Answer 1

您可以使用create_from_file()方法打开这些图像，并将其复制到将要显示的其他Pixbuf中。下面是我的代码:

DrawingArea.h

#ifndef DRAWINGAREA_H
#define DRAWINGAREA_H
#include <gtkmm.h>

class DrawingArea : public Gtk::DrawingArea
{
public:
    DrawingArea();
protected:
    // Override default signal handler:
    virtual bool on_draw(const Cairo::RefPtr<Cairo::Context>& cr);
private:
    // 1.Pgm image
    Glib::RefPtr<Gdk::Pixbuf> image1;
    // 2.Pgm image
    Glib::RefPtr<Gdk::Pixbuf> image2;
    //Pixel buffer for display
    Glib::RefPtr<Gdk::Pixbuf> display;
    // Scale of the image
    double scale;
};
#endif // DRAWINGAREA_H

DrawingArea.cpp

#include "DrawingArea.h"
DrawingArea::DrawingArea()
{
    // Load the images
    image1 = Gdk::Pixbuf::create_from_file("first.pgm");
    image2 = Gdk::Pixbuf::create_from_file("second.pgm");
    //create a 720x640 rgb Pixbuf
    display = Gdk::Pixbuf::create(Gdk::COLORSPACE_RGB,0,8,720,640);
}
// Call when the display need to be updated
bool DrawingArea::on_draw(const Cairo::RefPtr<Cairo::Context>& cr)
{
    //copy the two images to the display Pixbuf with this function:
    //void Gdk::Pixbuf::copy_area   (int src_x,int src_y,int width,int height,const Glib::RefPtr< Gdk::Pixbuf >& dest_pixbuf,int dest_x,int dest_y)     
    image1->copy_area(0,0,360,640,display,0,0);
    image2->copy_area(0,0,360,640,display,360,0);
    // Place the display Pixbuf at the center of the window
    Gdk::Cairo::set_source_pixbuf(cr, display, 0,0);
    // Update the whole drawing area
    cr->rectangle(0, 0, display->get_width(), display->get_height());
    // Fill the area with the image
    cr->fill();
    // The event has been handled.
    return true;
}

和main.cpp

#include <DrawingArea.h>
#include <gtkmm.h>

int main(int argc, char* argv[])
{
    // Initialize gtkmm and create the main window
    Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "betontaplfa");
    Gtk::Window window;
    // Create the drawing
    DrawingArea Dwg;
    // Insert the drawing in the window
    window.add(Dwg);
    // Resize the window
    window.resize(720,640);
    // Set the window title
    window.set_title("Pgm");
    // Show the drawing
    Dwg.show();
    // Start main loop
    return app->run(window);
}