I have image inside the JPanel. I would like to rotate the image. Is it possible to rotate the JPanel using Graphics, Image is rotatable, Just out of curiosity is it possible to rotate JPanel ?
Yes! This is possible and fairly straightforward too. I haven't done rotations but I have done other affine transformations (scaling the entire GUI up and down) very successfully on a project. I cannot see why rotations should be any different.
Instead of trying to scale each component use the fact that you can set a transformation on the Graphics object. Since this is shared between all components being rendered you get all things transformed at once "for free". It is important to realize that the transformation is only a rendering-process-step ... i.e. all components still believe they have the bounds (locations+sizes) which you gave them in the untransformed world. This leaves us with the challenge to deal with mouse-events correctly. To do this you simply add a glass-pane in front of your main-panel. This pane collects all mouse-events and apply a reverse of the transform on the event and then sends the event onward towards all other components.
Conceptually very simple! Still, I remember it took some tweaking to get it all crisp though. Especially the fact that rendered texts (fonts) in java are not correctly linearly scaled (it scales in discrete steps corresponding to font-sizes) imposed a final challenge in my scale-affine-transformation-case. Maybe you don't have to worry about that if you only rotate.
I got my inspiration from JXTransformer: http://www.java.net/blog/alexfromsun/archive/2006/07/jxtransformer_t.html
As far as I know you can't rotate a JPanel itself but you might be able to rotate the image inside the JPanel using Java2D. Here's an article that might help.
Edit:
There might actually be a way to rotate JComponents (such as JPanel) if you override their paintXxx methods and use AffineTransform.
It's not possible to rotate JPanel itself, but it's certainly possible to rotate any image inside. There are quite a few ways to do that, you can - for example - override JPanel's public void paint(Graphics g) and then cast Graphics to Graphics2D. It's very useful class, does rotation and much more ;) Check api docs for more info about this one.
Yes, it is possible. But you won't rotate the panel, but the image:
public void paintComponent(Graphics gg)
{
Graphics2D g = (Graphics2D) gg;
g.setRenderingHint(RenderingHints.KEY_ANTI_ALIAS, RenderingHints.VALUE_ANTI_ALIAS_ON);
AfflineTransform matrix = g.getTransform(); // Backup
float angle = Math.PI / 4.0f; // 45°
g.rotate(angle);
/* Begin */
g.drawImage(yourImage, [your coordinates], null);
/* End */
g.setTranform(matrix); // Restore
}
Everything between /* Begin */ and /* End */ will be drawn rotated.
(I didn't test the code, so, they may be some syntax errors...)
Related
Very simple question, but I could not find the answer in JavaFX docs or StackOverflow:
I have a JavaFX Canvas filled with a graph (various calls to strokeLine(), not the issue here). I need to be able to draw a rectangle over this graph, then simply clear the rectangle, without affecting the graph in the background. (Like an undo operation).
Code to draw the rectangle ('p' and 'e' are points):
gc.rect(p.getX(), p.getY(), e.getX()-p.getX(), e.getY()-p.getY());
gc.stroke();
The most obvious answer would be to use the clearRect() method, but the problem is that it clears also the portion of the graph in the background...
So the question is: how do I clear a drawing that was made with stroke(), without affecting the other drawings in the background?
You can't do this with one canvas.
Canvas only store the result of your painting operation.
This is the interest of the canvas you can stroke million times the same line and it will only store and represent the result and doesn't consume more memory.
So you if you need to draw Something over your chart you should put an other canvas over the chart and draw on the second canvas.
It might be more straight forward and much more the JavaFX-way of doing things if you just put your canvas into a Group and then just add a Rectangle node to the Group which you can remove at any time if you want.
This can be acheaved by taking snapshot(s) of your Canvas, using the .snapshot(SnapshotParameters params, WritableImage image) method. Basicly, every time you draw something on your Canvas, you take a snapshot of it and store it somewhere (for example in a ArrayList). Then you can use those snapshots to create a 'undo' operation, by using the . drawImage(Image img, double x, double y) method of Canvas's GraphicsContext, in which you would pass the snapshot you want to go back to as the Image parameter.
I have a rather pressing question in regards to Swing, which I haven't touched for many years.
I have a code that allows the user to draw different rectangles on the pdf document (contained within JPanel). I draw them, move them, resize them, select them, and even write text on them. What I can't do is to keep them consistent when I zoom the document. As the document gets bigger, the rectangles I've drawn stay at the same position and the same size.
I was wondering if there's a relatively easy logic to track the zooming level and, most importantly, update the rectangles accordingly. I can retrieve zoom factor, it's a float, but, unfortunately, I'm using Rectangle object, which uses int for x, y, height, and width. It will be a hassle to convert it to Rectangle.Float, and I wanted to save it for a last resort.
I've tried to use AffineTransform, but I'm not quite familiar with it, for some reason I'm getting the wrong coordinates for y. Can anyone explain to me:
What's the best way to control the Rectangle object, as the pdf document gets zoomed in and out?
If AffineTransform is the best way, how should I handle it (maybe there's a link to a good explanation, if so - I couldn't find it)?
This is the only issue I've been struggling with and it's getting a bit frustrating now.
To scale using an AffineTransform:
Get the transform T of the Graphics object G
Create an AffineTransform object A
Set the scale of A
Set the transform of the G to A
Draw the shapes
Set the transform of G back to T
Translated into code - assuming scale is the value to scale by:
#Override
protected void paintComponent(Graphics gr){
super.paintComponent(gr);
Graphics2D g = (Graphics2D)gr;
AffineTransform prevTransform = g.getTransform();
AffineTransform at = new AffineTransform(prevTransform);
at.scale(scale, scale);
g.setTransform(at);
g.drawRect(...);
g.setTransform(prevTransform);
}
I'm not quite sure how to phrase this, so bear with me.
I have two JPanels in a container JPanel with an OverlayLayout. Both JPanels in the container override paint(Graphics).
The bottom JPanel is opaque and draws some fairly complicated graphics, so it takes a "long" time (10s or 100s of milliseconds) to render.
The top JPanel is transparent and just draws a rectangle or line or simple shape based on mouse input, so it's really quick.
Is there a way to set things up so when I change the simple shape in the upper panel, it doesn't redraw the bottom panel? (e.g. it somehow caches the bottom panel)
I'm vaguely familiar w/ concepts like bitblt, double-buffering, and XOR-drawing but not really sure what to apply here.
You'd be best off using a single JComponent and creating a BufferedImage to store the bottom image. When the paintComponent operation happens on the JComponent, you just blit the bottom image and use the Graphics object to do any further drawing on top of that (from a stored state). Should be fairly efficient.
You'll want to do the complex drawing operations for the bottom BufferedImage in another thread, as the other poster mentions (omitted this by accident, sorry :)). However, you don't want to cause contention on this image, so you must store an additional BufferedImage for this, and blit it synchronously to the other image at the very moment the drawing operations are complete on it.
Focusing on the complicated panel, the key is factoring everything out of paintComponent() except drawImage(). Put everything else in another thread that continually updates an offscreen buffer. Periodically update the screen at some rate that keeps the simple panel responsive. The only hard part is synchronizing, but SwingWorker is a good choice. There's more here.
What's sure is that if the upper panel is target for a full repaint(), then the lower one will be also.
Maybe you can try to optimize the region to repaint on the upper panel in order to avoid repainting all the lower one. But if the painted rectangle in the upper panel covers the whole area, then you end up with full repaint() once again.
Normally, Swing tries to optimize the regions that need a repaint, but it also aggregates these regions when several repaint are performed in a short time, and if I remember well, the aggregated region is just a rectangle that is the union of all repaint rectangles, which is not always optimized but allows for fast computation of repaint events creation.
Now, I think you should follow the advices given in previous replies; indeed, you should really avoid having a paint() method that can perform computations that can be that long (a few 10s of ms should be the real maximum). Painting should be as fast as possible if you don't want to have a GUI that looks unresponsive to the end user. Hence, favour performing the computation only once (and outside the EDT if possible) store the result in a BufferedImage that you just simply draw later on in the paint() method.
EDIT: added other sources of reflection
If you want to optimize the update of the list of points but still keep it in the paint() method, then you can use the clipping region of the passed Graphics to limit the calls to drawing methods, something like:
Rectangle clip = g.getClipBounds();
for (Point p: allPoints) {
if (clip.contains(p)) {
// draw p with g graphics
}
}
You can even try to optimize the list of points to draw by using a QuadTree instead of a simple List, but you'll have to code it yourself (or find some free implementations, there are probably a few of them out there). With a quadtree, you can optimize the time to find the list of all points that have to be redrawn (based on the Graphics clipping rectangle) and only redraw those points.
Addenda for answer by trashgod and jfpoilpret
1/ OverlayLayout is strange way how to layout JPanels, are you same output with once JPanel (without OverlayLayout and Translucentcy)
2/ (10s or 100s of milliseconds) is maybe small value because there is Native OS Latency (45-75ms for today OS and PC)
3/ synchronizations would be managed by using SwingWorker on BackGround Task and with order, directions and synchronizations for painting processes to the JPanel, maybe your paints are too fast/quickly
4/ you didn't describe more about how, where and which about paint()/paintComponent()
if (SwingUtilities.isEventDispatchThread()) {
paintImmediately(int x, int y, int w, int h) // or Rectangle r
} else {
Runnable doRun = new Runnable() {
#Override
public void run() {
repaint(long tm, int x, int y, int width, int height) // or Rectangle r
}
};
SwingUtilities.invokeLater(doRun);
}
I'm Basically programming a simple game engine but I'm having problems with my sprites/images not appearing when they should... or at all!
I'll try and keep this as simple as possible. I have a Sprite, GameEngine and Display class. In the gameloop, I have a method that sets the new position of my Sprite (so it just sets the x and y variables). Next I call a transform method which does the following:
public void transform() {
affineTransform.setToIdentity();
affineTransform.translate(x, y);
}
Following that, I then call a draw method in the Sprite:
public void draw() {
graphics2D.drawImage(image, affineTransform, jFrame);
}
Finally, in my thread I then call repaint() on the JFrame (the Display class). My paint method for that class is as follows:
public void paint(Graphics g) {
g.drawImage(backbuffer, insets.left, insets.top, this);
}
But nothing is appearing, apart from a black screen!
I'm also getting confused between Graphics g, and Graphics2D and when to use either. (The overridden paint method uses Graphics g). For the record, I do have a Graphics2D variable in the class that is created by calling backbuffer.createGraphics();
Another thing that is confusing me is this AffineTransform... I've read the documentation but I'm still utterly confused on how and when to use it - and what exactly it seems to do. Is there any explanation in relatively simple terms?
Surely this should be working... am I missing something out here?
To answer part of your question:
From the Graphics2D JavaDoc
This Graphics2D class extends the Graphics class to provide more sophisticated control over geometry, coordinate transformations, color management, and text layout. This is the fundamental class for rendering 2-dimensional shapes, text and images on the Java(tm) platform.
Essentially, with Graphics2D you can do much more than you can with Graphics. And with a Sun JVM 1.5+, it should be safe to cast the Graphics object you get in paint() to Graphics2D
I just noticed this: For the record, I do have a Graphics2D variable in the class that is created by calling backbuffer.createGraphics();
You should make sure you're not drawing on a Graphics[2D] canvas (I'll use this term to refer to the drawable area that the Graphics[2D] object provides) that you later throw away. If you're drawing your image on a separate canvas, you should ensure that you then draw that image onto your actual display canvas.
I don't really have a good explanation of AffineTransform but maybe these will help?
http://www.javalobby.org/java/forums/t19387.html
https://secure.wikimedia.org/wikipedia/en/wiki/Affine_transformation
From Wikipedia - In general, an affine transformation is composed of linear transformations (rotation, scaling or shear) and a translation (or "shift"). Several linear transformations can be combined into a single one. Basically, you use this class to perform operations such as rotation, translation, zoom etc.
We have an old (more than 10yrs old) Java Swing applicatin which draws lots of circles and connections (lines) between those circles on a JCanvas (a subclass of JComponent) based on lab data.
Because the data becames bigger and bigger, we cannot display the entire drawing now. We have put the JCavans into a JScrollPane but it is not convenience to scroll the drawing.
Can we add zoom in zoom out for it? if yes, how? I know we can zoom image but the drawing on Canvas is an image?
thanks,
EDIT:
we draw those circles and line with Graphics within paintComponent(Graphics g) method.
You could apply a scaling Transform to the Graphics2D object passed to the paintComponent method. You can learn how to use it in the Java 2D programming trail.
Without knowing anything about your application it's hard to provide useful advice (adding a code snippet or better yet a cutdown example app would be helpful to show how things are being drawn), but I'll give it a shot:
Why don't you multiply the x,y and width,height values by a scaling factor before you draw each circle/line? I assume that somewhere your canvas is using a Graphics object to draw each shape?