Develop Reference

how to draw erase strokes programmatically using Samsung Pen SDK

I am using the pen SDK 4.0.7
I want to erase strokes programatically, pretty much the same thing a user will do with his finger or pen when the eraser is enabled.
I know that this code is used to draw pen strokes programatically:
SpenObjectStroke strokeObj = new SpenObjectStroke(penName, points, pressures, timestamps);
strokeObj.setPenSize(size);
strokeObj.setColor(color);
mSpenPageDoc.appendObject(strokeObj);
mSpenSurfaceView.update();
So my question is: how do I draw an Eraser stroke? (that cleans all the pen stokes it overlaps)

The solution I implemented was to use the MagicPen which has the capability of erasing a stroke when the intensity is set to the max value.
String penName = SpenPenManager.SPEN_MAGIC_PEN;
float penSize = eraserSettingView.getInfo().size;
int penColor = -16777216; // gotten from the max transparent color value of the Magic pen
SpenObjectStroke strokeObj = new SpenObjectStroke(penName, points, pressures, timestamps);
strokeObj.setPenSize(size);
strokeObj.setColor(color);
mSpenPageDoc.appendObject(strokeObj);
mSpenSurfaceView.update();

i have got two android draw but i dont know why one work and second not

This code work and draw a ok:
paintComponent(canvas);
p=new Paint();
p.setColor(Color.RED);
for(int i=1;i<pointA.size();i++){
int beginx=pointA.get(i-1).x, beginy=pointA.get(i-1).y,endx= pointA.get(i).x,endy= pointA.get(i).y;
canvas.drawLine(beginx,beginy ,endx,endy, p);
Log.e("matej",beginx+"endy"+beginy+"endx"+endx+"endy"+endy);
}
//canvas.drawLine(0, 181, xtest, ytest, p);
//canvas.drawPath(path, p);
This code drawing not good all draw from one point but i dont know why:
paintComponent(canvas);
p=new Paint();
p.setColor(Color.RED);
Path path1=new Path();
path1.moveTo(pointA.get(0).x, pointA.get(0).y);
for(int i=1;i<pointA.size();i=i+2){
int beginx=pointA.get(i-1).x, beginy=pointA.get(i-1).y,endx= pointA.get(i).x,endy= pointA.get(i).y;
path1.moveTo(pointA.get(i-1).x,pointA.get(i-1).y);
path1.lineTo(pointA.get(i).x, pointA.get(i).y);
Log.e("matej","beginx "+beginx+"beginy "+beginy+"endx "+endx+"endy "+endy);
And finly i want to know what i fail in second code and i want know which code is faster :) tnx

You declare lots of int values (beginx, beginy, etc) and don't actually use them, I'd suggest using them or deleting them for clarity.
You're also skipping out some points, IE
i = 1:
moveTo(0, 0)
lineTo(1, 1)
i = 3:
moveTo(2, 2)
lineTo(3, 3)
So no line is drawn between (1,1) and (2,2)
You also never call canvas.drawPath() so I'm not entirely sure how anything is getting drawn to the screen in the second example.

How to Detect a collition during animation?

I successfully made an arrow to move along a pre-defined path. Now i want to place some randomly moving object in the path and want to detect weather the arrow hits the object or not. The following is the code which i'm using for animation.
public void doAnimation(){
Matrix mxTransform=new Matrix();
PathMeasure pm=new PathMeasure(path,false);
float fSegmentLen = (float)((pm.getLength())/50);
if(iCurStep<=50){
pm.getMatrix(fSegmentLen * iCurStep, mxTransform,
PathMeasure.POSITION_MATRIX_FLAG + PathMeasure.TANGENT_MATRIX_FLAG);
canvas.drawBitmap(bt, mxTransform, null);
iCurStep++;
invalidate();
}
else{
iCurStep=0;
animate=0;
canvas.drawPoint((float)range-10,0f,forPoint);
}
}
The variable iCurStep is declared globally and the above function will be called inside the onDraw() method. I'm a beginner to android. So its very difficult for me to code. So I'm kindly requesting you to help me.

You can do this way as get the current position of the Arrow and moving objects.At any point of time, check its x-ordinates of Arrow intersects with x-coordinates of moving object.And similarly check for its y co-ordinates as well.
Hope this will help you.

How to add text to image and save as new image

I'm trying to create an Android app that adds a random quote to images.
The general process is this:
Start from a custom given image that shows when starting the app.
From this image all the user can do is tap on it and generate a new random "quote" that get overlaid on the image.
The user can save the newly created image with the quote he chose and set it as wallpaper.
I have got to the point where I can display the image in an ImageView.
My list of quotes is stored in my strings.xml file.

I do something like this in an app. Use Canvas.
I edited down a piece of my code, which actually adds a couple of other images on the background and stuff too.
Meat of code:
private static Bitmap getPoster(...) {
Bitmap background = BitmapFactory.decodeResource(res, background_id)
.copy(Bitmap.Config.ARGB_8888, true);
Canvas canvas = new Canvas(background);
Typeface font = Typeface.createFromAsset(res.getAssets(), FONT_PATH);
font = Typeface.create(font, Typeface.BOLD);
Paint paint = new Paint();
paint.setTypeface(font);
paint.setAntiAlias(true);
paint.setColor(Color.WHITE);
paint.setStyle(Style.FILL);
paint.setShadowLayer(2.0f, 1.0f, 1.0f, Color.BLACK);
float fontSize = getFontSize(background.getWidth(), THE_QUOTE, paint); //You'll have to define a way to find a size that fits, or just use a constant size.
paint.setTextSize(fontSize);
canvas.drawText(THE_QUOTE, (background.getWidth() - paint.measureText(THE_QUOTE)) / 2,
background.getHeight() - FILLER_HEIGHT, paint); //You might want to do something different. In my case every image has a filler in the bottom which is 50px.
return background;
}
Put your own version of that in a class and feed it the image id and anything else. It returns a bitmap for you to do whatever you want with (display it in an imageview, let the user save it and set as wallpape).

I know i did this for the PC with imagemagick a few years ago(save image with text on)
Seems like imagemagick have been ported to android, so I would start digging into thier documentation.
https://github.com/lilac/Android-ImageMagick

Ok! Francesco my friend, I've an idea although not a working code ('cuz I'm not really good at it). So, here it is:
Implement an onClickListener() on your ImageView like below:
ImageView iv = (ImageView)findViewById(R.id.imageview1);
iv.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v)
{
/** When I say do your stuff here, I mean read the user input and set your wallpaper here. I'm sorry that I don't really know how to save/set the wallpaper */
}
});
When it comes to reading user input/generating random quotes, you can do this:
You said you already have the quotes saved in the strings.xml file. Using the ids of those strings, I think you can implement a switch case scenario where it uses java imports - java.util.Scanner and java.util.Random. Ultimately, using these in your ImageView onClickListener could/should result in the desired output.
I know my answer is too vague, but I've a faint hope that it has given you a minute lead as to what you can implement. I seriously hope there are better answers than this. If not, then I hope this helps you some, and I also hope that I'm not leading you in the wrong direction since this is just a mere speculation. Sorry, but this is all I've got.

How can I tell if a closed path contains a given point?

In Android, I have a Path object which I happen to know defines a closed path, and I need to figure out if a given point is contained within the path. What I was hoping for was something along the lines of
path.contains(int x, int y)
but that doesn't seem to exist.
The specific reason I'm looking for this is because I have a collection of shapes on screen defined as paths, and I want to figure out which one the user clicked on. If there is a better way to be approaching this such as using different UI elements rather than doing it "the hard way" myself, I'm open to suggestions.
I'm open to writing an algorithm myself if I have to, but that means different research I guess.

Here is what I did and it seems to work:
RectF rectF = new RectF();
path.computeBounds(rectF, true);
region = new Region();
region.setPath(path, new Region((int) rectF.left, (int) rectF.top, (int) rectF.right, (int) rectF.bottom));
Now you can use the region.contains(x,y) method.
Point point = new Point();
mapView.getProjection().toPixels(geoPoint, point);
if (region.contains(point.x, point.y)) {
// Within the path.
}
** Update on 6/7/2010 **
The region.setPath method will cause my app to crash (no warning message) if the rectF is too large. Here is my solution:
// Get the screen rect. If this intersects with the path's rect
// then lets display this zone. The rectF will become the
// intersection of the two rects. This will decrease the size therefor no more crashes.
Rect drawableRect = new Rect();
mapView.getDrawingRect(drawableRect);
if (rectF.intersects(drawableRect.left, drawableRect.top, drawableRect.right, drawableRect.bottom)) {
// ... Display Zone.
}

The android.graphics.Path class doesn't have such a method. The Canvas class does have a clipping region that can be set to a path, there is no way to test it against a point. You might try Canvas.quickReject, testing against a single point rectangle (or a 1x1 Rect). I don't know if that would really check against the path or just the enclosing rectangle, though.
The Region class clearly only keeps track of the containing rectangle.
You might consider drawing each of your regions into an 8-bit alpha layer Bitmap with each Path filled in it's own 'color' value (make sure anti-aliasing is turned off in your Paint). This creates kind of a mask for each path filled with an index to the path that filled it. Then you could just use the pixel value as an index into your list of paths.
Bitmap lookup = Bitmap.createBitmap(width, height, Bitmap.Config.ALPHA_8);
//do this so that regions outside any path have a default
//path index of 255
lookup.eraseColor(0xFF000000);
Canvas canvas = new Canvas(lookup);
Paint paint = new Paint();
//these are defaults, you only need them if reusing a Paint
paint.setAntiAlias(false);
paint.setStyle(Paint.Style.FILL);
for(int i=0;i<paths.size();i++)
{
paint.setColor(i<<24); // use only alpha value for color 0xXX000000
canvas.drawPath(paths.get(i), paint);
}
Then look up points,
int pathIndex = lookup.getPixel(x, y);
pathIndex >>>= 24;
Be sure to check for 255 (no path) if there are unfilled points.

WebKit's SkiaUtils has a C++ work-around for Randy Findley's bug:
bool SkPathContainsPoint(SkPath* originalPath, const FloatPoint& point, SkPath::FillType ft)
{
SkRegion rgn;
SkRegion clip;
SkPath::FillType originalFillType = originalPath->getFillType();
const SkPath* path = originalPath;
SkPath scaledPath;
int scale = 1;
SkRect bounds = originalPath->getBounds();
// We can immediately return false if the point is outside the bounding rect
if (!bounds.contains(SkFloatToScalar(point.x()), SkFloatToScalar(point.y())))
return false;
originalPath->setFillType(ft);
// Skia has trouble with coordinates close to the max signed 16-bit values
// If we have those, we need to scale.
//
// TODO: remove this code once Skia is patched to work properly with large
// values
const SkScalar kMaxCoordinate = SkIntToScalar(1<<15);
SkScalar biggestCoord = std::max(std::max(std::max(bounds.fRight, bounds.fBottom), -bounds.fLeft), -bounds.fTop);
if (biggestCoord > kMaxCoordinate) {
scale = SkScalarCeil(SkScalarDiv(biggestCoord, kMaxCoordinate));
SkMatrix m;
m.setScale(SkScalarInvert(SkIntToScalar(scale)), SkScalarInvert(SkIntToScalar(scale)));
originalPath->transform(m, &scaledPath);
path = &scaledPath;
}
int x = static_cast<int>(floorf(point.x() / scale));
int y = static_cast<int>(floorf(point.y() / scale));
clip.setRect(x, y, x + 1, y + 1);
bool contains = rgn.setPath(*path, clip);
originalPath->setFillType(originalFillType);
return contains;
}

I know I'm a bit late to the party, but I would solve this problem by thinking about it like determining whether or not a point is in a polygon.
http://en.wikipedia.org/wiki/Point_in_polygon
The math computes more slowly when you're looking at Bezier splines instead of line segments, but drawing a ray from the point still works.

For completeness, I want to make a couple notes here:
As of API 19, there is an intersection operation for Paths. You could create a very small square path around your test point, intersect it with the Path, and see if the result is empty or not.
You can convert Paths to Regions and do a contains() operation. However Regions work in integer coordinates, and I think they use transformed (pixel) coordinates, so you'll have to work with that. I also suspect that the conversion process is computationally intensive.
The edge-crossing algorithm that Hans posted is good and quick, but you have to be very careful for certain corner cases such as when the ray passes directly through a vertex, or intersects a horizontal edge, or when round-off error is a problem, which it always is.
The winding number method is pretty much fool proof, but involves a lot of trig and is computationally expensive.
This paper by Dan Sunday gives a hybrid algorithm that's as accurate as the winding number but as computationally simple as the ray-casting algorithm. It blew me away how elegant it was.
See https://stackoverflow.com/a/33974251/338479 for my code which will do point-in-path calculation for a path consisting of line segments, arcs, and circles.