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Home » U++ Library support » Draw, Display, Images, Bitmaps, Icons » PATCH: Image load progress update
PATCH: Image load progress update [message #4828] Wed, 23 August 2006 11:06 Go to next message
aroman is currently offline  aroman
Messages: 18
Registered: November 2005
Promising Member

Loading large images can be slow (1+ sec), and in some applications it's nice to have a responsive UI during this time. I added a progress callback to the image loading code. The interface is the same except that loading functions now optionally take an additional progress callback.

This can be used very simply with:
Progress progress_window("Loading big image");
Image im = StreamRaster::LoadFileAny("big_image.jpg",progress_window);


Here is an example program that demonstrates both loading images and using the callback:
#include <CtrlLib/CtrlLib.h>

// NOTE: In order to load JPEG images, you need to include the "plugin\jpg" package!  Once that
// is included, you are all set to go.

// Example 1: This just loads and displays the file "image_to_load.jpg" in the directory of
// the executable.  It probably won't work if you run it without having that file, so I made
// the slightly fancier version below where you can pick a file.
//
// This version is here so that you can see the bare minimum code necessary to load and
// display an image.
class ReallySimpleImageViewer : public TopWindow {
public:
  ReallySimpleImageViewer() {
    // Set up our window to be resizeable
    Zoomable().Sizeable().Title("Simple Image Viewer");

    // Add a control that can display images.
    Label image_display;
    image_display.SetPaintRect(PaintRect(ImageDisplay()));
    image_display.AddFrame(ThinInsetFrame());
    Add(image_display.HSizePosZ(5,5).VSizePosZ(5,5));

    // While loading the image, we'll show a nice progress box so that the user
    // can cancel if they get bored.  This is optional!  If you leave out the
    // second parameter to "LoadFileAny", it will load the image until it finishes
    // or an error occurs.
    Progress progress_window("Loading image");
    Image im = StreamRaster::LoadFileAny("image_to_load.jpg",progress_window);

    // im will be either the image we tried to load or a null image if the load failed.
    // We can check for that with "IsNullInstance()"
    if (im.IsNullInstance())
      PromptOK("Could not load image");

    // Display the image. Won't display anything for a null image.
    image_display.SetImage(im);
  }
};

// Example 2: This allows the user to choose an image to load.
class SimpleImageViewer : public TopWindow {
public:
  typedef SimpleImageViewer CLASSNAME; // Necessary for THISBACK()
  MenuBar menu;
  StatusBar status;
  Label image_display;

  SimpleImageViewer() {
    Zoomable().Sizeable().Title("Simple Image Viewer");
    AddFrame(menu);
    menu.Set(THISBACK(MainMenu));
    AddFrame(status);

    image_display.SetPaintRect(PaintRect(ImageDisplay()));
    image_display.AddFrame(ThinInsetFrame());
    Add(image_display.HSizePosZ(5,5).VSizePosZ(5,5));
  }
  void MainMenu(Bar& bar) {
    bar.Add("File",THISBACK(FileMenu));
  }
  void FileMenu(Bar& bar) {
    bar.Add("Open image...",THISBACK(OpenImage));
    bar.Add("Exit",THISBACK(Close));
  }
  void OpenImage() {
    FileSel	fs;
    fs.Type("Image files","*.jpg,*.png,*.bmp");
    fs.AllFilesType();
    fs.ActiveDir(GetFileDirectory(GetDataFile("x")));
    if (fs.ExecuteOpen("Select image to load")) {
      String filename = fs.GetFile(0);
      status = Format("Loading [%s]",filename);
      Image im = StreamRaster::LoadFileAny(filename,Progress("Loading image"));
      if (im.IsNullInstance()) {
        status = Format("Failed to load [%s]",filename);
      } else {
        status = Format("Loaded [%s]",filename);
      }
      image_display.SetImage(im);
    }
  }
};

GUI_APP_MAIN
{
  SimpleImageViewer().Run();
}


Attached is the patch to add the necessary functionality.
Re: PATCH: Image load progress update [message #4841 is a reply to message #4828] Wed, 23 August 2006 13:12 Go to previous messageGo to next message
mirek is currently offline  mirek
Messages: 12098
Registered: November 2005
Ultimate Member
Good idea. Added (but I think you have a small error there, I have changed it to:

	ImageBuffer b(cx, yy - y);
	RGBA* t = b;
	int y0 = y; // <<<!
	while(y < yy) {
		if(progress(y - y0, yy - y0)) // <<<!
			return Null;
		memcpy(t, ~GetLine(y) + x, cx * sizeof(RGBA));
		t += cx;
		y++;
	}


Mirek
Re: PATCH: Image load progress update [message #4842 is a reply to message #4841] Wed, 23 August 2006 13:17 Go to previous messageGo to next message
mirek is currently offline  mirek
Messages: 12098
Registered: November 2005
Ultimate Member
P.S.: IsNullInstance is just "implementation" of "IsNull" (IsNull gets there via IsNull template). I have intended that you use

if(IsNull(image))


instead of

if(image.IsNullInstance())


(all in all, you cannot do
int x; if(x.IsNullInstance())

)

BTW, the "Instance" postfix is there because otherwise there is name clash problem in methods od classes that implement IsNull too...

(think

struct Foo {
   int x;
   bool IsNull() { return IsNull(x); }
};


-> IsNull(x) would be resolved as Foo::IsNull)

Mirek
Re: PATCH: Image load progress update [message #4880 is a reply to message #4841] Thu, 24 August 2006 04:09 Go to previous message
aroman is currently offline  aroman
Messages: 18
Registered: November 2005
Promising Member

luzr wrote on Wed, 23 August 2006 04:12

Good idea. Added (but I think you have a small error there, I have changed it to:



Good catch -- thanks, and thanks for the info about IsNull().

- Augusto
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