Show certain image from image sprite - c++

I have wrote a class which will be responsible for the image buttons handling:
#include "ImageButton.h"
ImageButton::ImageButton()
{
// main constructor
}
ImageButton::ImageButton(wxWindow* parent, const wxString& buttonPath)
: wxStaticBitmap(parent, wxID_ANY, wxBitmap(buttonPath, wxBITMAP_TYPE_PNG), wxPoint(0, 0), wxDefaultSize)
{
Refresh();
}
ImageButton::~ImageButton()
{
// ...
}
This is very beginning and basic. However, I have just found out that there is probably no possibility to resize the image (not changing it's dimensions).
This is how the image looks like:
What I'd like to achieve right here is tell wxStaticBitmap to display only one close square button at the time (so then I could make a mouse over/click event handlers for it). Setting it's size won't work here and thats not what I want.
Is it possible to crop the image at certain dimensions in this situation?

You can create two images from it. One of the ways to do it is to use wxImage::Resize (first make a copy of the original image). Second way is to use wxBitmap::GetSubBitmap (you need to convert the wxImage to wxBitmap - this can be done by simple assignment). It really depends what you want to achieve and what is more convenient to you.

Related

GTKMM: Take a screen shot of an DrawingArea?

I Have a Drawing Area that I draw some figures or images inside, so I have this callback to take screenshots:
void CanvasToolBox::actionCanvasCamera()
{
auto root = Gdk::Window::get_default_root_window();
int height = root->get_height();
int width = root->get_width();
auto pixels = Gdk::Pixbuf::create(root, 0, 0, width, height);
pixels->save("s.png", "png");
}
That code takes a screenshot of the whole screen..
But I need to take the screenshot of a especific window a Gtk::DrawingArea in my case.. so the function create needs a Gdk::Window as a parameter.
Is there any way to take a screenshot of a Gtk especific window?
Thanks
I'm not used to GTKmm (I use C and Python APIs instead), but with your example, that looks pretty straightforward. You just want to use your Gtk::DrawingArea instead of the root window. So you search in the documentation of Gdk::Window::get_default_root_window and find that it returns a Gdk::Window.
Now you have to find how to get a Gdk::Window out of a Gtk::DrawingArea. So you go to the documentation of Gtk::DrawingArea and search for a function that returns a Gdk::Window, and then find this is Gtk::Widget::get_window, which is inherited from Gtk::Widget. BTW, you may prefer the const version, as you don't modify the window, just read it.
You can then replace code that gets the root windows with a call to get the Gdk::Window of the widget you care about, and you're done. If you want to go further, instead of using Gdk::Pixbuf, there may be a way to use a cairo context.

MFC Image Button with transparency

I'm updating an MFC dialog with a number of buttons on it.
At present, the dialog has a Picture control covering the whole dialog providing a patterned background. On top of that, each button is a CBitmapButton using (opaque) images carefully generated to match the area of background they cover.
It would obviously be much easier if the images could be created as mostly transparent, so the background shows through automatically. However, I can't work out how to get MFC to render transparent images correctly in this case.
I understand that I might want a different class to CBitmapButton, or need to write a custom subclass; that's fine, but I don't know where to start. It would be nice to support 32-bit BMP or PNG with alpha channel, but I'd settle for the "specified colour should be transparent" type.
It may not be the best way to do it, but what I'd do is create a custom CButton derived class (assuming that you're actually using the rest of the CButton functionality), then override the DrawItem function to put your custom draw code in.
For the image itself I'd use a Bitmap GDI+ object (which will allow you to load either BMPs or PNGs with alpha channels) then use the regular DrawImage function to draw the bitmap.
If you're going to put PNGs into your resource file then you need to put them in as a "PNG" type. Make sure when you look in the resource file code that the entry looks like
IDB_PNG1 PNG "C:\temp\test.png"
and doesn't try to treat it as a BITMAP resource otherwise you'll have problems loading them.
Edit
Putting my response here so I can post code. Yes, I meant to derive a custom class from CButton, then add a Gdiplus::Bitmap member variable. Here is roughly what you'll need to do to get it to work, though I haven't checked that the code actually compiles and works, but hopefully you'll get the idea. It's not the most efficient way to do it, but if you've not done much custom drawing before then it does have the advantage of being simple!
void CMyButton::LoadImage(const int resourceID)
{
m_pBitmap = Gdiplus::Bitmap::FromResource(NULL, MAKEINTRESOURCE(resourceID));
ASSERT(m_pBitmap);
}
void CMyButton::DrawItem(LPDRAWITEMSTRUCT lpDrawItemStruct)
{
ASSERT(lpDrawItemStruct->CtlType == ODT_BUTTON);
CRect rcClient;
GetClientRect(&rcClient);
if (lpDrawItemStruct->itemState & ODS_SELECTED)
{
// If you want to do anything special when the button is pressed, do it here
// Maybe offset the rect to give the impression of the button being pressed?
rcClient.OffsetRect(1,1);
}
Graphics gr(lpDrawItemStruct->hDC);
gr.DrawImage(m_pBitmap, rcClient.left, rcClient.top);
}

How to show part of an image using QT?

So, this is my problem: I have this very big image, and I want to show only a specific part of it. After the user pressing a specific key I want the image to move, showing another part of it. The transition from one part of the image to another have to be smooth, animated.
I tried using a QLabel to show the image but it always shows the center of the image, and I do not really know how to make the animation. What would you guys suggest?
Interesting question. Here is something I just tested and seems to work.
Add a QGraphicsView with dimensions the dimensions of the part of the image you want to display, eg 100x100. Create a QGraphicsScene and add it to the view:
QGraphicsScene* pScene = new QGraphicsScene(this);
ui->graphicsView->setScene(pScene);
Now add your image into the scene. In my case I has an image in my resource file. The trick is to set the sceneRect to the position you want to display. I wanted to display an 100x100 part of the image starting from 0,300 :
pItem = pScene->addPixmap(QPixmap::fromImage(QImage(":/photos/image")));
pScene->setSceneRect(0,300,100,100);
In order to test the smooth moving I added a button which when clicked is triggering a slot called move. This slot simply updates the sceneRect. In my simple example I just move the image 100 pixels right. In a real world scenario you could also move it diagonally or vertically and check the image limits.
void move()
{
for (unsigned i=currentX; i<currentX + 100; i++)
{
ui->graphicsView->scene()->setSceneRect(i,300,100,100);
qApp->processEvents();
}
currentX += 100;
}
Notice the currentX variable. It is nothing more than the last image position. Also we must call the processEvents in order to "see" the image moving smoothly.
You could use QPixmap::copy( int x, int y, int width, int height ) to copy a region of the image and display that.
Few options:
Try using a Q3CanvasSprite (within in a Q3Canvas). It is designed more for splitting one image into multiple ones but not for animating between them. You could try abusing it and declaring (say) 100 frames (10 per digit, which would be used as animation steps) or just use the move() method.
Try QGraphicsPixmapItem::setOffset() (within a QGraphicsScene). This might be overkill as QGraphicsScene is made for large number of images).
I'm not sure, but maybe this can be done with QStateMachine and QAbstractAnimation.

How to save to a bitmap in MFC C++ application?

I am just starting with MFC so please be tolerant ;).
I have wrote (it was mostly generated to be honest) a simple application which should do the Paint chores: drawing lines, rectangulars, ellipses, changing a color of object to be drawn etc.
I need to save what has been drawn on the screen into a bmp file. Any ideas how can I achieve this ?
I do not know if that's relevant but I am drawing objects on the screen without the use of any CBitmaps or things like that. Here is a part of code responsible for drawing :
CPaintDoc* pDoc = GetDocument();
ASSERT_VALID(pDoc);
Anchor.x=point.x;
Anchor.y=point.y;
OldPoint.x=Anchor.x;
OldPoint.y=Anchor.y;
if(pDoc->shapeCount>=MAX_SHAPES) return;
pDoc->shapeCount++;
if(bFreehand)
{
pDoc->m_shape[pDoc->shapeCount-1] = new Shape;
pDoc->m_shape[pDoc->shapeCount-1]->shape = ePoint;
}
if(bLine)
{
pDoc->m_shape[pDoc->shapeCount-1] = new CLine;
pDoc->m_shape[pDoc->shapeCount-1]->shape = eLine;
}
if(bRectangle)
{
pDoc->m_shape[pDoc->shapeCount-1] = new CRectangle;
pDoc->m_shape[pDoc->shapeCount-1]->shape = eRectangle;
}
if(bEllipse)
{
pDoc->m_shape[pDoc->shapeCount-1] = new CEllipse;
pDoc->m_shape[pDoc->shapeCount-1]->shape=eEllipse;
}
pDoc->m_shape[pDoc->shapeCount-1]->x=point.x;
pDoc->m_shape[pDoc->shapeCount-1]->y=point.y;
pDoc->m_shape[pDoc->shapeCount-1]->x2=point.x;
pDoc->m_shape[pDoc->shapeCount-1]->y2=point.y;
pDoc->m_shape[pDoc->shapeCount-1]->Pen=CurrentPen;
pDoc->m_shape[pDoc->shapeCount-1]->Brush=CurrentBrush;
bButtonDown=true;
SetCapture();
I have found this way to do it but I don't know how to obtain screen width and height to fill it in the CreateBitmap parameter's list
CBitmap *bitmap;
bitmap.CreateBitmap(desktopW, desktopH, 1, 32, rgbData);
CImage image;
image.Attach(bitmap);
image.Save(_T("C:\\test.bmp"), Gdiplus::ImageFormatBMP);
The CreateBitmap call only requires the desktop width and height if the image you wish to save is actually the entire size of the screen. If that's indeed your intent, you can use CWnd::GetDesktopWindow() to get a CWnd object that you can query for its width and height:
http://msdn.microsoft.com/en-us/library/bkxb36k8(v=VS.80).aspx
That gets dodgy in general...if for no other reason than multi-monitor scenarios...so I'd recommend against it unless you really feel like writing a screen capture app.
What you probably want to do isn't to take a full screen shot, but just save the contents of your program's window. Typically you'd do this by breaking out the drawing logic of your program so that in the paint method you call a helper function that is written to take a CDC device context. Then you can either call that function on the window-based DC you get in the paint call or on a DC you create from the bitmap to do your save. Note that you can use a CBitmap in CDC::SelectObject:
http://msdn.microsoft.com/en-us/library/432f18e2(v=VS.71).aspx
(Though let me pitch you on not using MFC. Try Qt instead. Way better.)

Tiling with QGraphicsScene and QGraphicsView

I'm creating a image visualizer that open large images(2gb+) in Qt.
I'm doing this by breaking the large image into several tiles of 512X512. I then load a QGraphicsScene of the original image size and use addPixmap to add each tile onto the QGraphic Scene. So ultimately it looks like a huge image to the end user when in fact it is a continuous array of smaller images stuck together on the scene.First of is this a good approach?
Trying to load all the tiles onto the scene takes up a lot of memory. So I'm thinking of only loading the tiles that are visible in the view. I've already managed to subclass QGraphicsScene and override its drag event thus enabling me to know which tiles need to be loaded next based on movement. My problem is tracking movement on the scrollbars. Is there any way I can create an event that get called every time the scrollbar moves. Subclassing QGraphicsView in not an option.
QGraphicsScene is smart enough not to render what isn't visible, so here's what you need to do:
Instead of loading and adding pixmaps, add classes that wrap the pixmap, and only load it when they are first rendered. (Computer scientists like to call this a "proxy pattern"). You could then unload the pixmap based on a timer. (They would be transparently re-loaded if unloaded too soon.) You could even notify this proxy path of the current zoom level, so that it loads lower resolution images when they will be rendered smaller.
Edit: here's some code to get you started. Note that everything that QGraphicsScene draws is a QGraphicsItem, (if you call ::addPixmap, it's converted to a ...GraphicsItem behind the scenes), so that's what you want to subclass:
(I haven't even compiled this, so "caveat lector", but it's doing the right thing ;)
class MyPixmap: public QGraphicsItem{
public:
// make sure to set `item` to nullptr in the constructor
MyPixmap()
: QGraphicsItem(...), item(nullptr){
}
// you will need to add a destructor
// (and probably a copy constructor and assignment operator)
QRectF boundingRect() const{
// return the size
return QRectF( ... );
}
void paint(QPainter *painter, const QStyleOptionGraphicsItem *option,
QWidget *widget){
if(nullptr == item){
// load item:
item = new QGraphicsPixmapItem( ... );
}
item->paint(painter, option, widget);
}
private:
// you'll probably want to store information about where you're
// going to load the pixmap from, too
QGraphicsPixmapItem *item;
};
then you can add your pixmaps to the QGraphicsScene using QGraphicsScene::addItem(...)
Although an answer has already been chosen, I'd like to express my opinion.
I don't like the selected answer, especially because of that usage of timers. A timer to unload the pixmaps? Say that the user actually wants to take a good look at the image, and after a couple of seconds - bam, the image is unloaded, he will have to do something in order the image to reappear. Or may be you will put another timer, that loads the pixmaps after another couple of seconds? Or you will check among your thousand of items if they are visible? Not only is this very very irritating and wrong, but that means that your program will be using resources all the time. Say the user minimizes you program and plays a movie, he will wonder why on earth my movie is freezing every couple of seconds...
Well, if I misunderstood the proposed idea of using timers, execuse me.
Actually the idea that mmutz suggested is better. It reminded me of the Mandelbrot example. Take a look at it. Instead of calculating what to draw you can rewrite this part to loading that part of the image that you need to show.
In conclusion I will propose another solution using QGraphicsView in a much simpler way:
1) check the size of the image without loading the image (use QImageReader)
2) make your scene's size equal to that of the image
3) instead of using pixmap items reimplement the DrawBackground() function. One of the parameters will give you the new exposed rectangle - meaning that if the user scrolls just a little bit, you will load and draw only this new part(to load only part of an image use setClipRect() and then read() methods of the QImageReader class). If there are some transformations you can get them from the other parameter(which is QPainter) and apply them to the image before you draw it.
In my opinion the best solution will be to combine my solution with the threading shown in the Mandelbrot example.
The only problem that I can think of now is if the user zooms out with a big scale factor. Then you will need a lot of resources for some time to load and scale a huge image. Well I see now that there is some function of the QImageReader that I haven't tried yet - setScaledSize(), which maybe do just what we need - if you set a scale size and then load the image maybe it won't load first the entire image – try it. Another way is just to limit the scale factor, a thing that you should do anyway if you stick to the method with the pixmap items.
Hope this helps.
Unless you absolutely need the view to be a QGraphicsView (e.g. because you place other objects on top of the large background pixmap), I'd really recommend just subclassing QAbstractScrollArea and reimplementing scrollContentsBy() and paintEvent().
Add in a LRU cache of pixmaps (see QPixmapCache for inspiration, though that one is global), and make the paintEvent() pull used pixmaps to the front, and be set.
If this sounds like more work than the QGraphicsItem, believe me, it's not :)