Develop Reference

Thresholding in Android using opencv

Not sure if this is the right way to ask, but please help. I have an image of a dented car. I have to process it and highlight the dents and return the number of dents. I was able to do it reasonably well with the following result:
The matlab code is:
img2=rgb2gray(i1);
imshow(img2);
img3=imtophat(img2,strel('disk',15));
img4=imadjust(img3);
layer=img4(:,:,1);
img5=layer>100 & layer<250;
img6=imfill(img5,'holes');
img7=bwareaopen(img6,5);
[L,ans]=bwlabeln(img7);
imshow(img7);
I=imread(i1);
Ians=CarDentIdentification(I);
However, when I try to do this using opencv, I get this:
With the following code:
Imgproc.cvtColor(source, middle, Imgproc.COLOR_RGB2GRAY);
Imgproc.equalizeHist(middle, middle);
Imgproc.threshold(middle, middle, 150, 255, Imgproc.THRESH_OTSU);
Please tell me how can I obtain better results in opencv, and also how to count the dents? I tried findcontour() but it gives a very large number. I tried on other images as well, but I'm not getting proper results.
Please help.

So you basically from the MATLAB site, imtophat does - Top-hat filtering computes the morphological opening of the image (using imopen) and then subtracts the result from the original image.
You could do this in OpenCV with the following steps:
Step 1: Get the disk structuring element
kernel = cv2.getStructuringElement(cv2.MORPH_ELLIPSE, (15, 15))
Step 2: Compute opening of the image and then subtract the result from the original image
tophat = cv2.morphologyEx(v, cv2.MORPH_TOPHAT, kernel)
This gives following result -
Step 3 - Now you could just manually threshold it or use Otsu -
ret, thresh = cv2.threshold(tophat, 17, 255, 0)
which gives you the following image -
Since the OP wants the code in Java, here is the probable code in Java:
private Mat topHat(Mat image)
{
Mat element = Imgproc.getStructuringElement(Imgproc.MORPH_ELLIPSE, new Size(15, 15), new Point (0, 0));
Mat dst = new Mat;
Imgproc.morphologyEx(image, dst, Imgproc.MORPH_TOPHAT, element, new Point(0, 0));
return dst;
}
Make sure you do this on a gray scale image (CvType.8UC1) and then you can threshold suitably.

Why is the drawContour() in OpenCV generating this strange Mask?

I started by reading in this Mat.
Then I converted it to Greyscale and applied Imgproc.canny() to it, getting the following mask.
Then I used Imgproc.findContours() to find the contours, Imgproc.drawContours(), and Core.putText() to label the contours with numbers:
Then I did Rect boundingRect = Imgproc.boundingRect(contours.get(0));
Mat submatrix = new Mat();
submatrix = originalMat.submat(boundingRect); to get following submatrix:
So far so good. The Problem starts hereafter:
NOW I NEEDED A MASK OF THE submatrix. So I decided to use Imgproc.drawContours() to get the mask:
Mat mask = new Mat(submatrix.rows(), submatrix.cols(), CvType.CV_8UC1);
List<MatOfPoint> contourList = new ArrayList<>();
contourList.add(contours.get(0));
Imgproc.drawContours(mask, contourList, 0, new Scalar(255), -1);
I got the following mask:
WHAT I WAS EXPECTING was a filled (in white color) diamond shape on black background.
WHy am I getting this unexpected result?
EDIT:
When I replaced Mat mask = new Mat(submatrix.rows(),
submatrix.cols(), CvType.CV_8UC1); by Mat mask =
Mat.zeros(submatrix.rows(), submatrix.cols(), CvType.CV_8UC1);,
the last mask with white colored garbage was replaced by an empty
black mask withOUT any white color on it. I got the following submat
and mask:
I was getting the first contour in the list of contours (named
contours) by contours.get(0), and using this first contour to
calculate Imgproc.boundingRect() as well as in
contourList.add(contours.get(0)); later (where contourList is
the list of just one contour which will be used in the last
drawContours()).
Then I went ahead to change contours.get(0) to
contours.get(1) in Imgproc.boundingRect() as well as in contourList.add(); (just before Imgproc.drawContours()). That
resulted in this submat and mask:
Then I changed back to contours.get(0) in
Imgproc.boundingRect(); and let
contourList.add(contours.get(1)); be there. Got the following
submat and mask:
NOW I am completely Unable to Understand what is happening here.

I am not sure how this is handle in JAVA (I usually use OpenCV in c++ or python), but there is an error in your code...
The contours list will have a list of list of points. This points will refer to the original image. So, this mean that if the figure one is in lets say, x=300, y= 300, width= 100, height=100 then when you get your submatrix it will try to draw those points in a smaller image... so when it tries to draw point (300,300) in a 100 x 100 image, it will simply fail... probably throws an error or simply doesn't draw anything...
A solution for this is, do a for loop and substract to each point of the contour the initial point of the bounding rect (in my example (300,300)).
As, why there is some garbage drawn... well you never initialize the matrix. Not sure in JAVA, but in c++ you have to set them to 0.
I think it should be something like this:
Mat mask = new Mat(submatrix.rows(), submatrix.cols(), CvType.CV_8UC1, new Scalar(0));
I hope this helps :)
EDIT
I think I did not explain myself clearly before.
Your contours are an array of points (x,y). These are the coordinates of the points that represent each contour in the original image. This image has a size, and your submatrix has a smaller size. The points are outside of this small image boundaries....
you should do something like this to fix it:
for (int j = 0; j < contours[0].length; j++) {
contours[0][j].x -= boundingrect.x;
contours[0][j].y -= boundingrect.y;
}
and then you can draw the contours, since they will be in boundaries of the submat.
I think in java it is also possible to subtract the opencv points directly:
for (int j = 0; j < contours[0].length; j++) {
contours[0][j] -= boundingrect.tl();
}
but in this case I am not sure, since I have tried it in c++ only
boundingrect.tl() -> gives you the top left point of the rect

Textures with programmable color in Rajawali

All works great for me with Rajawali in Android, except textures.
I would like to programmatically load a transparent image as a texture, with a chessboard pattern where each black square is in fact fully transparent while each white square is just white.
I would like to use this as a texture over an object, that otherwise has diffuse and specular color properties that can be changed programmatically. So if the user has inputted the color blue, I would like the object to show a blue-white pattern.
How can I do that?
The rajawali tutorials do not really help, since for textures rajawali changed a lot in the last update. Also the Rajawali examples app does not really help, as they all seem to deal with environment maps.
What I tried was e.g.:
protected void initScene() {
objParser = new LoaderOBJ(mContext.getResources(), mTextureManager, R.raw.stdblock_obj);
try{
Texture jetTexture = new Texture("jetTexture", R.drawable.chessboardtexture);
mTextureManager.getInstance().addTexture(jetTexture);
semiglossMaterial.addTexture(jetTexture);
semiglossMaterial.setColorInfluence(0);
}catch(TextureException e){
e.printStackTrace();
}
}
The object is rendered, but without any texture. The chessboard image does have a size power-of-2, and it is located in the right folder R.raw.stdblock_obj. It is a jpg image, but I also tried png which didn't work either.
I also tried a different approach:
semiglossMaterial.enableLighting(true);
semiglossMaterial.setDiffuseMethod(new DiffuseMethod.Lambert());
phongMethod.setShininess(iShininess); semiglossMaterial.addTexture(new Texture("jetTexture",R.drawable.chessboardtexture));
semiglossMaterial.addTexture(new AlphaMapTexture("alphaMapTex", R.drawable.simpletexture3));
semiglossMaterial.setColorInfluence(0);
but also this did not work.
Anyone an idea?

You have to add that texture as a child, a child of the .obj file, if you don´t know how many child have your .obj and the name of them, use:
"your3DobjectName".numChildren(),
then use a simple
for(int i = 0; i < "your3DobjectName".numChildren(); i++)
{
String name = "your3DobjectName".getChildAt(i).name();
Log.d("rajawali", "Name: "+name);
}
At this way you will know how many childs and the name of your childs declared at your obj

why detected object jumps using OpenCV

Ok I have a strange problem. I'll try to describe it as best as I can.
I've learned my app to detect a car when looking on it from the side
Imgproc.cvtColor(aInputFrame, grayscaleImage, Imgproc.COLOR_RGBA2RGB);
MatOfRect objects = new MatOfRect();
// Use the classifier to detect cars
if (cascadeClassifier != null) {
cascadeClassifier.detectMultiScale(grayscaleImage, objects, 1.1, 1,
2, new Size(absoluteObjectSize, absoluteObjectSize),
new Size());
}
for (int i = 0; i < dataArray.length; i++) {
Core.rectangle(aInputFrame, dataArray[i].tl(), dataArray[i].br(),
new Scalar(0, 255, 0, 255), 3);
mRenderer.setCameraPosition(-5, 5, 60f);
}
Now, this code works nice. I mean that i detects cars and it marks them with green rectangle. The problem is that the marked rectangle jumps like hell. I mean even when the phone is hold still the rectangle jumps from left to right to middle. There is never one still rectangle. I hope I've described the problem properly. I would like to stabilizy the marking cause I want to draw an overlay based on it and I can't make it to jump like this

See(1) the parameters for detectMultiScale and it expects
image of type CV_8U. You will need to convert to gray scale image
with COLOR_RGBA2GRAY instead of COLOR_RGBA2RGB
In detectMultiScale, increase the number of neighbours parameter to avoid false positives.
Suggestion: If input is a video stream, don't run
detectMultiScale on every frame. It is slow even if you use LBP
cascades. Try detection in one frame, followed by tracking techniques.

how to merge Images and impose on each other

Suppose I'm uploading two or more than two pics in some Framelayout. Hereby I'm uploading three pics with a same person in three different position in all those three pictures. Then what image processing libraries in Android or java or Native's are available to do something as shown in the pic.
I would like to impose multiple pictures on each other.
Something like these:-
One idea is to :
Do some layering in all those pictures and find mismatching areas in the pics and merge them.
How one can merge multiple picture with other? By checking the di-similarity and merge with each other?
Are there any Third party Api's or some Photoshop service which can help me in doing these kinda image processing?

In this case you are not just trying to combine the images. You really want to combine a scene containing the same object in different positions.
Therefore, it is not just a simple combination or an alpha compositve where the color of a given pixel in the output image is the sum of the value of this pixel in each image, divided by the number of images.
In this case, you might do:
Determine the scene background analysing the pixels that do not change considering multiple images.
Begin with the output image being just the background.
For each image, remove the background to get the desired object and combine it with the output image.
There is a Marvin plug-in to perform this task, called MergePhoto. The program below use that plug-in to combine a set of parkour photos.
import marvin.image.MarvinImage;
import marvin.io.MarvinImageIO;
import marvin.plugin.MarvinImagePlugin;
import marvin.util.MarvinPluginLoader;
public class MergePhotosApp {
public MergePhotosApp(){
// 1. load images 01.jpg, 02.jpg, ..., 05.jpg into a List
List<MarvinImage> images = new ArrayList<MarvinImage>();
for(int i=1; i<=5; i++){
images.add(MarvinImageIO.loadImage("./res/0"+i+".jpg"));
}
// 2. Load plug-in and process the image
MarvinImagePlugin merge = MarvinPluginLoader.loadImagePlugin("org.marvinproject.image.combine.mergePhotos");
merge.setAttribute("threshold", 38);
// 3. Process the image list and save the output
MarvinImage output = images.get(0).clone();
merge.process(images, output);
MarvinImageIO.saveImage(output, "./res/merge_output.jpg");
}
public static void main(String[] args) {
new MergePhotosApp();
}
}
The input images and the output image are shown below.

I don't know if this will qualify to be in your definition of "natives", but there is the following .NET library that could help: http://dynamicimage.apphb.com/
If the library itself can give you want you want, then depending on your architecture you could set up a small ASP.NET site to do the image manipulation on the server.

Check the accepted answer here.
In above link there is merging of two images which is done by openCV sdk.
If you dont want to use openCV and just want to try with your self then you will have to play little with framlayout and with three imageview. Give options to user to select specific part of the image to show for all three images. So the selected part will be shown of the selected image. on this way you will get the result like above what you have said.
Hope you got my point. If not then let me know.
Enjoy coding... :)

You can overlay the images using openCV you can check at OpenCV and here or here
// Read the main background image
cv::Mat image= cv::imread("Background.png");
// Read the mans character image to be placed
cv::Mat character= cv::imread("character.png");
// define where you want to place the image
cv::Mat newImage;
//The 10,10 are the initial coordinates in pixels
newImage= image(cv::Rect(10,10,character.cols,character.rows));
// add it to the background, The 1 is the aplha values
cv::addWeighted(newImage,1,character,1,0,newImage);
// show result
cv::namedWindow("with character");
cv::imshow("with character",image);
//Write Image
cv::imwrite("output.png", newImage);
or you can create it as a watermark effect
Or you can try it in java like merging two images
try using this class
public class MergeImages {
public static void main(String[] args) {
File inner = new File("Inner.png");
File outter = new File("Outter.png");
try {
BufferedImage biInner = ImageIO.read(inner);
BufferedImage biOutter = ImageIO.read(outter);
System.out.println(biInner);
System.out.println(biOutter);
Graphics2D g = biOutter.createGraphics();
g.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.8f));
int x = (biOutter.getWidth() - biInner.getWidth()) / 2;
int y = (biOutter.getHeight() - biInner.getHeight()) / 2;
System.out.println(x + "x" + y);
g.drawImage(biInner, x, y, null);
g.dispose();
ImageIO.write(biOutter, "PNG", new File("Outter.png"));
} catch (Exception e) {
e.printStackTrace();
}
}
}