when i draw a lot of lines, the apps takes a long time to finish drawing. My goal is to connecting of the points in a1[] to form a line. Is there is faster way of doing this? please help!
> $ for (int i = 0; i < x.length - 1; i++) {
> _canvas.drawLine(a1[i].x, a1[i].y, a1[i + 1].x, a1[i + 1].y,_paint);}
Use draw lines. Pack the points into a float[] with 2 points for each point in the line then do this:
if (count >= 4) {
if ((count & 2) != 0) {
canvas.drawLines(pointlist, 0, count-2, linePaint);
canvas.drawLines(pointlist, 2, count-2, linePaint);
}
else {
canvas.drawLines(pointlist, 0, count, linePaint);
canvas.drawLines(pointlist, 2, count - 4, linePaint);
}
}
Where count is the number usable length in the float[] of points. Drawlines goes by 4 floats per segment, but if you stagger them like that you get the result you want without needing to waste 2x the memory and you can effectively move the points if need be.
Use Canvas.drawLines(float[] pts, Paint paint);
Using Canvas.drawLines instead of Canvas.drawLine i have halved the time of drawing.
I have to draw 12 lines with 5000 points for line and the time of drawing with this code is 2393 milliseconds instead of 6000 milliseconds using Canvas.drawLine() method.
int lineIndex = 0;
float[] lines = new float[a1.length * 4];
for (int i = 0; i < a1.length-1; i++) // -1 to deal with last point
{
lines[lineIndex++] = a1[i].x;
lines[lineIndex++] = a1[i].y;
lines[lineIndex++] = a1[i + 1].x
lines[lineIndex++] = a1[i + 1].y;
}
_canvas.drawLines(lines, _paint);
Try creating a Path first, then calling _canvas.drawPath():
Path p = new Path();
p.moveTo(a1[0].x, a1[0].y);
for (int i = 1; i < x.length; i++) {
p.lineTo(a1[i].x, a1[i].y);
}
_canvas.drawPath(p, _paint);
Related
game.batch.begin();
for (Array obstacle_array123: obstacle_array) {
body = obstacle_array123;
for (Body bodies: body) {
if (bodies.getUserData() instanceof Array && bodies.isActive()) {
sprites_array = (Array)bodies.getUserData();
for (int fix_pos = 0; fix_pos < sprites_array.size; fix_pos++) {
sprite = sprites_array.get(fix_pos);
if (verts.size != 0) verts.removeRange(0, verts.size - 1);
f = bodies.getFixtureList().get(fix_pos);
s = (PolygonShape)f.getShape();
transform = bodies.getTransform();
for (int i = 0; i < s.getVertexCount(); i++)
{
s.getVertex(i, tmp);
transform.mul(tmp);
verts.add(new Vector2(tmp));
}
rotation_point.set((verts.get(0).x + verts.get(1).x + verts.get(2).x + verts.get(3).x) / 4, (verts.get(0).y + verts.get(1).y + verts.get(2).y + verts.get(3).y) / 4);
sprite.setPosition(rotation_point.x - sprite.getWidth() / 2, rotation_point.y - sprite.getHeight() / 2);
sprite.setRotation(bodies.getAngle() * MathUtils.radiansToDegrees);
sprite.draw(game.batch);
}
}
}
}
game.batch.end();
I have a game where my bodies are made from multiple square fixtures, so this is the code to render each square sprite on each square fixture.
2 problems - 1.st --> it only renders the first sprite in the array
2.nd --> if you look at the following loop (SOLVED)
for (int i = 0; i < s.getVertexCount(); i++)
{
s.getVertex(i, tmp);
transform.mul(tmp);
verts.add(new Vector2(tmp));
}
well it is apperantly different compared to
for (int i = 0; i < s.getVertexCount(); i++)
{
s.getVertex(i, tmp);
transform.mul(tmp);
verts.add(tmp);
}
The spawned coordinates in 2nd example are wrong for half width and half height of the square.
When I try to get the coordinated from both examples the numbers are the same, but when setting the sprite position, 2nd example goes off.
You should probably ask both questions separately, but to answer your second question, then they ARE different.
In the first one you add a new Vector2 to verts each time through the loop. So verts will end up holding a load of different Vector2's.
In the second one you add the same Vector2 to verts over and over again, so it will just have one Vector2 with the same value over and over again (remember Java is pass by reference).
Caveat - My answer assumes that verts is some sort of standard collection or a libgdx Array.
I'd like to examine each Canny detected edge and look for the main lines in it (to check if they seem to shape a rectangle, for example if 2 pairs of lines are parallel etc.).
Imgproc.HoughLinesP does what I want, but it gives the lines from the whole image, and I want to know which lines come from the same edges.
I tried also FindContours, and looking for main lines in each contour with approxPolyDP, but this doesn't look adapted because there are often gaps in Canny detected edges. This gives contours of the edges and not the edges themselves.
Here is a test image example :
How can I get a set of lines for each shape ?
Based on Miki's answer, here is what I've done :
Canny
HoughLinesP (or LineSegmentDetector, as you want) : to detect lines
ConnectedComponents : to find Canny "contours" in the Canny image.
Dilate with a 3x3 kernel (see below)
For each Hough line : take a few pixels from the line and look for the most frequent value (ignore 0's).
For example, I chose {p1 , 0.75*p1 + 0.25*p2, 0.5*p1 + 0.5*p2, 0.25*p1 + 0.75*p2, p2}, so if my values are {1,2,0,2,2} then the line belongs to the connectedComponent number 2.
Dilating is to be sure you didn't miss a contour by only 1 pixel (but don't use it if your objects are too close).
This allows to "tag" HoughLines with the color of the contour they belong to.
All of these functions can be found in Imgproc module, this works in OpenCV 3.0 only and gives the desired result.
Here is a code :
// open image
File root = Environment.getExternalStorageDirectory();
File file = new File(root, "image_test.png");
Mat mRGBA = Imgcodecs.imread(file.getAbsolutePath());
Imgproc.cvtColor(mRGBA, mRGBA, Imgproc.COLOR_BGR2RGB);
Mat mGray = new Mat();
Imgproc.cvtColor(mRGBA, mGray, Imgproc.COLOR_RGBA2GRAY);
Imgproc.medianBlur(mGray, mGray, 7);
/* Main part */
Imgproc.Canny(mGray, mGray, 50, 60, 3, true);
Mat aretes = new Mat();
Imgproc.HoughLinesP(mGray, aretes, 1, 0.01745329251, 30, 10, 4);
/**
* Tag Canny edges in the gray picture with indexes from 1 to 65535 (0 = background)
* (Make sure there are less than 255 components or convert mGray to 16U before)
*/
int nb = Imgproc.connectedComponents(mGray,mGray,8,CvType.CV_16U);
Imgproc.dilate(mGray, mGray, Imgproc.getStructuringElement(Imgproc.MORPH_RECT, new Size(3,3)));
// for each Hough line
for (int x = 0; x < aretes.rows(); x++) {
double[] vec = aretes.get(x, 0);
double x1 = vec[0],
y1 = vec[1],
x2 = vec[2],
y2 = vec[3];
/**
* Take 5 points from the line
*
* x----x----x----x----x
* P1 P2
*/
double[] pixel_values = new double[5];
pixel_values[0] = mGray.get((int) y1, (int) x1)[0];
pixel_values[1] = mGray.get((int) (y1*0.75 + y2*0.25), (int) (x1*0.75 + x2*0.25))[0];
pixel_values[2] = mGray.get((int) ((y1 + y2) *0.5), (int) ((x1 + x2) *0.5))[0];
pixel_values[3] = mGray.get((int) (y1*0.25 + y2*0.75), (int) (x1*0.25 + x2*0.75))[0];
pixel_values[4] = mGray.get((int) y2, (int) x2)[0];
/**
* Look for the most frequent value
* (To make it readable, the following code accepts the line only if there are at
* least 3 good pixels)
*/
double value;
Arrays.sort(pixel_values);
if (pixel_values[1] == pixel_values[3] || pixel_values[0] == pixel_values[2] || pixel_values[2] == pixel_values[4]) {
value = pixel_values[2];
}
else {
value = 0;
}
/**
* Now value is the index of the connected component (or 0 if it's a bad line)
* You can store it in an other array, here I'll just draw the line with the value
*/
if (value != 0) {
Imgproc.line(mRGBA,new Point(x1,y1),new Point(x2,y2),new Scalar((value * 41 + 50) % 255, (value * 69 + 100) % 255, (value * 91 + 60) % 255),3);
}
}
Imgproc.cvtColor(mRGBA, mRGBA, Imgproc.COLOR_RGB2BGR);
File file2 = new File(root, "image_test_OUT.png");
Imgcodecs.imwrite(file2.getAbsolutePath(), mRGBA);
If you're using OpenCV 3.0.0 you can use LineSegmentDetector, and "AND" your detected lines with the contours.
I provide a sample code below. It's C++ (sorry about that), but you can easily translate in Java. At least you see how to use LineSegmentDetector and how extract common lines for each contour. You'll see the lines on the same contour with the same color.
#include <opencv2/opencv.hpp>
using namespace cv;
using namespace std;
int main()
{
RNG rng(12345);
Mat3b img = imread("path_to_image");
Mat1b gray;
cvtColor(img, gray, COLOR_BGR2GRAY);
Mat3b result;
cvtColor(gray, result, COLOR_GRAY2BGR);
// Detect lines
Ptr<LineSegmentDetector> detector = createLineSegmentDetector();
vector<Vec4i> lines;
detector->detect(gray, lines);
// Draw lines
Mat1b lineMask(gray.size(), uchar(0));
for (int i = 0; i < lines.size(); ++i)
{
line(lineMask, Point(lines[i][0], lines[i][1]), Point(lines[i][2], lines[i][3]), Scalar(255), 2);
}
// Compute edges
Mat1b edges;
Canny(gray, edges, 200, 400);
// Find contours
vector<vector<Point>> contours;
findContours(edges.clone(), contours, CV_RETR_EXTERNAL, CV_CHAIN_APPROX_NONE);
for (int i = 0; i < contours.size(); ++i)
{
// Draw each contour
Mat1b contourMask(gray.size(), uchar(0));
drawContours(contourMask, contours, i, Scalar(255), 2); // Better use 1 here. 2 is just for visualization purposes
// AND the contour and the lines
Mat1b bor;
bitwise_and(contourMask, lineMask, bor);
// Draw the common pixels with a random color
vector<Point> common;
findNonZero(bor, common);
Vec3b color = Vec3b(rng.uniform(0, 255), rng.uniform(0, 255), rng.uniform(0, 255));
for (int j = 0; j < common.size(); ++j)
{
result(common[j]) = color;
}
}
imshow("result", result);
waitKey();
return 0;
}
I want to ask about some ideas / study materials connected to binarization. I am trying to create system that detects human emotions. I am able to get areas such as brows, eyes, nose, mouth etc. but then comes another stage -> processing...
My images are taken in various places/time of day/weather conditions. It's problematic during binarization, with the same treshold value one images are fully black, other looks well and provide me informations I want.
What I want to ask you about is:
1) If there is known way how to bring all images to the same level of brightness?
2) How to create dependency between treshold value and brightness on image?
What I have tried for now is normalize the image... but there are no effects, maybe I'm doing something wrong. I'm using OpenCV (for android)
Core.normalize(cleanFaceMatGRAY, cleanFaceMatGRAY,0, 255, Core.NORM_MINMAX, CvType.CV_8U);
EDIT:
I tried adaptive treshold, OTSU - they didnt work for me. I have problems with using CLAHE in Android but I managed to implement Niblack algorithm.
Core.normalize(cleanFaceMatGRAY, cleanFaceMatGRAY,0, 255, Core.NORM_MINMAX, CvType.CV_8U);
nibelBlackTresholding(cleanFaceMatGRAY, -0.2);
private void nibelBlackTresholding(Mat image, double parameter) {
Mat meanPowered = image.clone();
Core.multiply(image, image, meanPowered);
Scalar mean = Core.mean(image);
Scalar stdmean = Core.mean(meanPowered);
double tresholdValue = mean.val[0] + parameter * stdmean.val[0];
int totalRows = image.rows();
int totalCols = image.cols();
for (int cols=0; cols < totalCols; cols++) {
for (int rows=0; rows < totalRows; rows++) {
if (image.get(rows, cols)[0] > tresholdValue) {
image.put(rows, cols, 255);
} else {
image.put(rows, cols, 0);
}
}
}
}
The results are really good, but still not enough for some images. I paste links cuz images are big and I don't want to take too much screen:
For example this one is tresholded really fine:
https://dl.dropboxusercontent.com/u/108321090/a1.png
https://dl.dropboxusercontent.com/u/108321090/a.png
But bad light produce shadows sometimes and this gives this effect:
https://dl.dropboxusercontent.com/u/108321090/b1.png
https://dl.dropboxusercontent.com/u/108321090/b.png
Do you have any idea that could help me to improve treshold of those images with high light difference (shadows)?
EDIT2:
I found that my previous Algorithm is implemented in wrong way. Std was calculated in wrong way. In Niblack Thresholding mean is local value not global. I repaired it according to this reference http://arxiv.org/ftp/arxiv/papers/1201/1201.5227.pdf
private void niblackThresholding2(Mat image, double parameter, int window) {
int totalRows = image.rows();
int totalCols = image.cols();
int offset = (window-1)/2;
double tresholdValue = 0;
double localMean = 0;
double meanDeviation = 0;
for (int y=offset+1; y<totalCols-offset; y++) {
for (int x=offset+1; x<totalRows-offset; x++) {
localMean = calculateLocalMean(x, y, image, window);
meanDeviation = image.get(y, x)[0] - localMean;
tresholdValue = localMean*(1 + parameter * ( (meanDeviation/(1 - meanDeviation)) - 1 ));
Log.d("QWERTY","TRESHOLD " +tresholdValue);
if (image.get(y, x)[0] > tresholdValue) {
image.put(y, x, 255);
} else {
image.put(y, x, 0);
}
}
}
}
private double calculateLocalMean(int x, int y, Mat image, int window) {
int offset = (window-1)/2;
Mat tempMat;
Rect tempRect = new Rect();
Point leftTop, bottomRight;
leftTop = new Point(x - (offset + 1), y - (offset + 1));
bottomRight = new Point(x + offset, y + offset);
tempRect = new Rect(leftTop, bottomRight);
tempMat = new Mat(image, tempRect);
return Core.mean(tempMat).val[0];
}
Results for 7x7 window and proposed in reference k parameter = 0.34: I still can't get rid of shadow on faces.
https://dl.dropboxusercontent.com/u/108321090/b2.png
https://dl.dropboxusercontent.com/u/108321090/b1.png
things to look at:
http://docs.opencv.org/java/org/opencv/imgproc/CLAHE.html
http://docs.opencv.org/java/org/opencv/imgproc/Imgproc.html#adaptiveThreshold(org.opencv.core.Mat,%20org.opencv.core.Mat,%20double,%20int,%20int,%20int,%20double)
http://docs.opencv.org/java/org/opencv/imgproc/Imgproc.html#threshold(org.opencv.core.Mat,%20org.opencv.core.Mat,%20double,%20double,%20int) (THRESH_OTSU)
I am new to android and building an app which involves displaying a view for 2 seconds and then change. Here's my onDraw method:
#Override
public void onDraw(Canvas canvas)
{
float level = game.level;
width = getWidth();
tile_length = width/level;
Paint rect = new Paint();
rect.setColor(getResources().getColor(R.color.dark));
canvas.drawRect(0, 0, width, width, rect);
game.numbers.setTextSize( (0.70f * tile_length));
game.numbers.setTextAlign(Paint.Align.CENTER);
grid.setColor(getResources().getColor(R.color.lines));
rect.setColor(getResources().getColor(R.color.tile_on));
int ind = 1;
int tile_num = 1;
FontMetrics fm = game.numbers.getFontMetrics();
float x = tile_length/2;
float y = tile_length/2 - (fm.ascent + fm.descent) / 2;
Log.v(LOG_TAG, "changed = " + game.changed);
for (int i=0; i<width; i+=tile_length)
{
for(int j=0; j<width; j+=tile_length)
{
for(int k = 0; k<level; k++ )
if(tile_num == game.random[k])
{
// Log.v(LOG_TAG, "i = " + i + "j = " + j);
game.set_Coordinates(ind-1, i, j);
String tile = Integer.toString(ind++);
canvas.drawRect(i, j, i+tile_length, j+tile_length, rect);
canvas.drawText(tile, i+x, j+y, game.numbers); //needs to be updated after 2 seconds
break;
}
tile_num++;
}
}
}
I understand i have to use postdelayed method somewhere, but don't know how...Now i just want to ommit the canvas.drawText line after the delay.
do you mean something like this
new Handler().postDelayed(new Runnable(){
public void run(){
// do something here like draw text;
}
}, 2000);
A timer is needed, indeed. What I do, which is very simple, is first to create records of coordinates (and any other data needed) for every point of the drawing -- instead of drawing the points on the spot -- and then reproduce them using a timer (Android handler, preferably, like the one suggested above). This also offers you a lot of possibilities while actual drawing: pause, go faster/slower, go backwards, ...
I don't know if this method can be used for complicated drawings, but it is fine for drawing shapes, curves, surfaces, etc.
I have an isometric map which I draw to the canvas. When I try and move the map around, these black lines flicker in between some of the tiles making the whole thing look rather shoddy.
Here is the relevant code from my updating thread
public void run() {
Canvas c;
while (isRunning){
c = null;
try {
c = cellMap.getHolder().lockCanvas(null);
synchronized (cellMap.getHolder()) {
cellMap.onDraw(c);
}
} finally {
if( c != null){
cellMap.getHolder().unlockCanvasAndPost(c);
}
}
}
}
and from my CellMap class (which extends SurfaceView):
public void onDraw(Canvas canvas){
canvas.drawColor(Color.BLACK);
int x = 0;
int y = 0;
for(int i = 0; i < mapSize; i++){
for(int j = 0; j < mapSize; j++){
x = (i-j) * 30 + xOffset;
y = (i+j) * 15 + yOffset;
mapCells[i][j].draw(canvas, paint, x, y);
}
}
mapCells[][] is an array of objects which contain the Bitmap image that needs to be drawn. The draw() function is only 1 line canvas.drawBitmap(bitmapImage, x, y, null)
I have discovered that removing the line Canvas.draw(Color.black) gets rid of the flicker. However, when I move the map the canvas is not cleared so I still see the image from the previous frames. I'd imagine it is because it is taking too long to draw the bitmaps? but the map is only very small at the moment.
I found the problem. When moving the map, the offset values were being changed. This lead to sections of the map being drawn temporarily with different offset values - creating the tearing. duh!
I solved this by copying the xOffset and yOffset values at the start of the onDraw() method, and using those values for the update.