How to Draw a Continuous Line on Java

I am writing a 2D traditional animation program in Java using swing and JPen. The application works well. However, i am dissatisfied with the results I am getting when I draw lines.

Using the JPen API, the swing panel listens for the stylus input and its code is:

                      /**  * This method is called whenever the stylus makes contact with the tablet while inside of the JPanel functioning  * as the Drawing Canvas.  * @param evt  */ public void penLevelEvent(PLevelEvent evt) {     // Get kind of event: does it come from mouse (CURSOR), STYLUS or ERASER?     PKind kind = evt.pen.getKind();      // Discard events from mouse     if (kind == PKind.valueOf(PKind.Type.CURSOR)){         //System.out.println("returning since this is only a mouse cursor");        return;      }       // Get the current cursor location     // position value is in with respect to entire application window     // Get the tilt values (not with a Bamboo... so untested!)     float curX      = evt.pen.getLevelValue(PLevel.Type.X);     float curY      = evt.pen.getLevelValue(PLevel.Type.Y);     float pressure  = evt.pen.getLevelValue(PLevel.Type.PRESSURE);// 0.0 - 1.0     float xTilt     = evt.pen.getLevelValue(PLevel.Type.TILT_X);     float yTilt     = evt.pen.getLevelValue(PLevel.Type.TILT_Y);      // Set the brush's size, and darkness relative to the pressure     float darkness = 255 * pressure;       // Transform them to azimuthX and altitude, two angles with the projection of the pen against the X-Y plane     // azimuthX is the angle (clockwise direction) between this projection and the X axis. Range: -pi/2 to 3*pi/2.     // altitude is the angle between this projection and the pen itself. Range: 0 to pi/2.     // Might be more pratical to use than raw x/y tilt values.     double[] aa = { 0.0, 0.0 };     PLevel.Type.evalAzimuthXAndAltitude(aa, xTilt, yTilt);     // or just PLevel.Type.evalAzimuthXAndAltitude(aa, evt.pen);     double azimuthX = aa[0];     double altitude = aa[1];      //-------------------------------------------------------------------------------------     // If the stylus is being pressed down, we want to draw a black     // line onto the screen. If it's the eraser, we want to create     // a white line, effectively "erasing" the black line     //-------------------------------------------------------------------------------------     if (kind == PKind.valueOf(PKind.Type.STYLUS)) {         //System.out.println("Darkness "+darkness);         int alpha = 255 - (int)darkness;         color = new Color(0,0,255,  255 - alpha);     }     else if (kind == PKind.valueOf(PKind.Type.ERASER)) {         System.out.println("Handle eraser");     }     else {         return; // IGNORE or CUSTOM...     }      //If movement of the stylus is occuring     if (evt.isMovement()) {         //and the buttonIsDown(boolean)         if(buttonIsDown) {             //drawingCanvas:JPanel -> instruct the jpanel to draw at the following coordinate using the specified pressure             drawingCanvas.stylusMovementInput( prevXPos,prevYPos, curX,curY, pressure);         }         prevXPos = curX;         prevYPos = curY;     }      prevXPos = curX;     prevYPos = curY;  }                  

So after the above method is invoked, the jpanel(drawingCanvas) starts to draw on a BufferedImage by obtaining the image's graphics2D. Here is the code stylusMovementInput->calls -> performDrawOnBufferImageGraphic2D :

          /**  * Draw on the active frame that is selected.  Then call channel refresh, to refresh the the composite image derived  * from call changes related to the current frame  * @param cX current  * @param cY current  * @param oX previous  * @param oY previous  * @param pressure pressure 0 - 1f  */ private void performDrawOnBufferImageGraphic2D(float oX, float oY, float cX, float cY, float pressure){     //Obtain the current layer that user wants to draw one     //MyImageData is encapsulating a BufferedImage     MyImageData $activeData = getActiveLayer();     //Exit if one is not valid     if( $activeData == null) return;     //if valid layer, get the, get the bufferedImage.getGraphics     Graphics2D $activeDataGFX = $activeData.getImageGraphics();       // Customize the drawing brush (create a BasicStroke)     Stroke thickness = Sys.makeStroke(getPencilSize(pressure), null);     // Determine the tranparency with respect to the pressure     int alpha = (int)(255 * pressure * getPencilOpacityPercentage());     // Get the current color found in the color wheel     Color cwVal = Sys.getColorFromColorWheel();      Color drawingColor ;     if(cwVal != null){         // add alpha value to it         drawingColor = new Color(cwVal.getRed(), cwVal.getGreen(), cwVal.getBlue(), alpha);      }else throw new RuntimeException("ColorWheel is null drawing stylus draw");      //set the brush and drawingColor     $activeDataGFX.setStroke(thickness);      // Save reference to the current bufferedImage graphic component     Composite originalComposite =$activeDataGFX.getComposite();     if(getCurrentTool() == DrawingCanvasTool.ERASER){         //If eraser,  set new composite information, to allow erasing to transparency         $activeDataGFX.setPaint( new Color(255,255,255, 0));         $activeDataGFX.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_IN, 0.0f));     }else {         //set the drawing color         $activeDataGFX.setPaint(drawingColor);     }       //---------------------------------------------------------------     // Rotate, Translate, Zoom the image according to the panning, zoom, and rotate     // set by the user     //---------------------------------------------------------------     //Figure out the canvas center, as it is used for rotating     float theta  = (float)Math.toRadians(canvasRotation);     Dimension drawingAreaComponentSize = getSize();     float centerX = drawingAreaComponentSize.width/2;     float centerY = drawingAreaComponentSize.height/2;     AffineTransform transform = new AffineTransform();     transform.rotate(-theta, centerX, centerY);     transform.scale(1.0f / canvasZoom, 1.0f / canvasZoom);//erase     transform.translate(-canvasPan.x, -canvasPan.y);//erase     $activeDataGFX.setTransform(transform);       //Now Draw inside of the active data graphics object       Shape line = new Line2D.Float(cX,cY, oX, oY);     Path2D.Float t = new Path2D.Float(line);     $activeDataGFX.draw(t);      //drawing is complete     if(getCurrentTool() ==DrawingCanvasTool.ERASER){         //Restore the old composite object         $activeDataGFX.setComposite(originalComposite);     }      //Refresh basically merges frames along a frame column into a single preview buffered image     //which will later be used to view the tool animation when user clicks "play" button     channelPannel.refreshFrameOut(  channelPannel.getCurrentFrame()  ); }                  

I commented a lot of the code, and provided the critical points related to the question. Any help is much appreciated. And again, the problem is how do i draw a smooth line worthy of a descent drawing program.

munroeforrout.blogspot.com

Source: https://stackoverflow.com/questions/32924112/how-to-draw-smooth-continuous-line-in-java-swing-that-also-varies-in-size

Share this post