I'm trying to detect a object using cvblob. So I use cvRenderBlob() method. Program compiled successfully but when at the run time it is returning an unhandled exception. When I break it, the arrow is pointed out to CvLabel *labels = (CvLabel *)imgLabel->imageData + imgLabel_offset + (blob->miny * stepLbl); statement in the cvRenderBlob() method definition of the cvblob.cpp file. But if I use cvRenderBlobs() method it's working fine. I need to detect only one blob that is the largest one. Some one please help me to handle this exception.
Here is my VC++ code,
CvCapture* capture = 0;
IplImage* frame = 0;
int key = 0;
CvBlobs blobs;
CvBlob *blob;
capture = cvCaptureFromCAM(0);
if (!capture) {
printf("Could not initialize capturing....\n");
return 1;
}
int screenx = GetSystemMetrics(SM_CXSCREEN);
int screeny = GetSystemMetrics(SM_CYSCREEN);
while (key!='q') {
frame = cvQueryFrame(capture);
if (!frame) break;
IplImage* imgHSV = cvCreateImage(cvGetSize(frame), 8, 3);
cvCvtColor(frame, imgHSV, CV_BGR2HSV);
IplImage* imgThreshed = cvCreateImage(cvGetSize(frame), 8, 1);
cvInRangeS(imgHSV, cvScalar(61, 156, 205),cvScalar(161, 256, 305), imgThreshed); // for light blue color
IplImage* imgThresh = imgThreshed;
cvSmooth(imgThresh, imgThresh, CV_GAUSSIAN, 9, 9);
cvNamedWindow("Thresh");
cvShowImage("Thresh", imgThresh);
IplImage* labelImg = cvCreateImage(cvGetSize(imgHSV), IPL_DEPTH_LABEL, 1);
unsigned int result = cvLabel(imgThresh, labelImg, blobs);
blob = blobs[cvGreaterBlob(blobs)];
cvRenderBlob(labelImg, blob, frame, frame);
/*cvRenderBlobs(labelImg, blobs, frame, frame);*/
/*cvFilterByArea(blobs, 60, 500);*/
cvFilterByLabel(blobs, cvGreaterBlob(blobs));
cvNamedWindow("Video");
cvShowImage("Video", frame);
key = cvWaitKey(1);
}
cvDestroyWindow("Thresh");
cvDestroyWindow("Video");
cvReleaseCapture(&capture);
First off, I'd like to point out that you are actually using the regular c syntax. C++ uses the class Mat. I've been working on some blob extraction based on green objects in the picture. Once thresholded properly, which means we have a "binary" image, background/foreground. I use
findContours() //this function expects quite a bit, read documentation
Descriped more clearly in the documentation on structural analysis. It will give you the contour of all the blobs in the image. In a vector which is handling another vector, which is handling points in the image; like so
vector<vector<Point>> contours;
I too need to find the biggest blob, and though my approach can be faulty to some extend, I won't need it to be different. I use
minAreaRect() // expects a set of points (contained by the vector or mat classes
Descriped also under structural analysis
Then access the size of the rect
int sizeOfObject = 0;
int idxBiggestObject = 0; //will track the biggest object
if(contours.size() != 0) //only runs code if there is any blobs / contours in the image
{
for (int i = 0; i < contours.size(); i++) // runs i times where i is the amount of "blobs" in the image.
{
myVector = minAreaRect(contours[i])
if(myVector.size.area > sizeOfObject)
{
sizeOfObject = myVector.size.area; //saves area to compare with further blobs
idxBiggestObject = i; //saves index, so you know which is biggest, alternatively, .push_back into another vector
}
}
}
So okay, we really only measure a rotated bounding box, but in most cases it will do. I hope that you will either switch to c++ syntax, or get some inspiration from the basic algorithm.
Enjoy.
Related
Image to be manipulated, hoping to identify each white dot on each picture with a counter
PImage blk;
void setup() {
size(640, 480);
blk=loadImage("img.png");
}
void draw () {
loadPixels();
blk.loadPixels();
int i = 0;
for (int x = 0; x < width; x++) {
for (int y = 0; y < height; y++) {
int loc = x+y*width;
pixels [loc] = blk.pixels[loc];
if (blk.pixels[loc] == 0) {
if (blk.pixels [loc]+1 != 0) {
i++;
}
}
float r = red(blk.pixels[loc]);
float g = green(blk.pixels[loc]);
float b = blue(blk.pixels[loc]);
pixels [loc] = color(r, g, b);
}
}
System.out.println (i);
updatePixels();
}
The main problem is within my if statement, not sure to approach it logically.
I'm unsure where this is exactly going, but I can help you find the white pixels. Here, I just counted 7457 "white" pixels (then I turned them red so you can see where they are and adjust the threshold if you want to get more or less of them):
Of course, this is just a proof of concept which you should be able to adapt to your needs.
PImage blk;
void setup() {
size(640, 480);
blk=loadImage("img.png");
blk.loadPixels();
int whitePixelsCount = 0;
// I'm doing this in the 'setup()' method because I don't need to do it 60 times per second
// Once it's done once I can just use the image as modified unless you want several
// different versions (which you can calculate once anyway then store in different PImages)
for (int i = 0; i < blk.width * blk.height; i++) {
float r = red(blk.pixels[i]);
float g = green(blk.pixels[i]);
float b = blue(blk.pixels[i]);
// In RGB, the brightness of each color is represented by it's intensity
// So here I'm checking the "average intensity" of the color to see how bright it is
// And I compare it to 100 since 255 is the max and I wanted this simple, but you can
// play with this threshold as much as you like
if ((r+g+b)/3 > 100) {
whitePixelsCount++;
// Here I'm making those pixels red so you can see where they are.
// It's easier to adjust the threshold if you can see what you're doing
blk.pixels[i] = color(255, 0, 0);
}
}
println(whitePixelsCount);
updatePixels();
}
void draw () {
image(blk, 0, 0);
}
In short (you'll read this in the comments too), we count the pixels according to a threshold we can adjust. To make things more obvious for you, I colored the "white" pixels red. You can lower or raise the threshold according to what you see this way, and once you know what you want you can get rid of the color.
There is a difficulty here, which is that the image isn't "black and white", but more greyscale - which is totally normal, but makes things harder for what you seem to be trying to do. You'll probably have to tinker a lot to get to the exact ratio which interests you. It could help a lot if you edited the original image in GiMP or another image software which lets you adjust contrast and brightness. It's kinda cheating, but it it doesn't work right off the bat this strategy could save you some work.
Have fun!
I have an image, read using "cv::imread". I have to flatten it so that I could use CUDA & GPU for my image processing algorithms acceleration.
My problem: When I read my image, I can show it correctly using imshow, however when I flatten it and convert it to a Mat object to be used with imshow, only part of my image is displayed. The size of the output image is also wrong, meaning that some data is really lost. What's the problem with my for loop?
// The problematic part of my code
// The Camera Man gray test image
const char* img_gray_name = "../../Test_Images/cameraman.tiff";
const char* img_blur_name = "../cameraman-blur.tiff";
const char* image_general_name = "cameraman_blur";
cv::Mat img = cv::imread(img_gray_name);
unsigned long int img_gray_size = img.rows * img.cols * sizeof(uchar);
uchar *h_img_in;// input image, converted to a flat array to be
// processed by GPU
h_img_in = (uchar *)malloc(img_gray_size);
//*************** The bug should be here! ***************//
for (int i = 0; i < img.rows; ++i) {
for (int j = 0; j < img.cols; ++j) {
h_img_in[i*img.cols+j] = img.at<uchar>(i, j);
}
}
Mat img_test;
img_test = Mat(cv::Size(img.cols, img.rows), CV_8U, h_img_in);
imwrite(img_blur_name, img_test);
// create image window named "camera man"
cv::namedWindow(image_general_name);
// show the image on window
cv::imshow(image_general_name, img_test);
P.S.: I also tested with a new 2D array instead of 1D h_img_in, result is the same; This means that something goes wrong with my usage of "img.at(i, j)".
How Can I add a song to this code using processing?, And synchronize it with a PIR sensor in Arduino?.
import processing.video.*;
import ddf.minim.*;
import ddf.minim.AudioPlayer;
// Size of each cell in the grid
int cellSize = 20;
// Number of columns and rows in our system
int cols, rows;
// Variable for capture device
Capture video;
Minim minim;
AudioPlayer song;
void setup() {
size(1280, 720);
frameRate(30);
cols = width / cellSize;
rows = height / cellSize;
colorMode(RGB, 255, 255, 255, 100);
// This the default video input, see the GettingStartedCapture
// example if it creates an error
video = new Capture(this, width, height);
// Start capturing the images from the camera
video.start();
background(0);
}
{
// we pass this to Minim so that it can load files from the data directory
minim = new Minim(this);
// loadFile will look in all the same places as loadImage does.
// this means you can find files that are in the data folder and the
// sketch folder. you can also pass an absolute path, or a URL.
song = minim.loadFile("untitled.wav");
}
void draw() {
if (video.available()) {
video.read();
video.loadPixels();
// Begin loop for columns
for (int i = 0; i < cols; i++) {
// Begin loop for rows
for (int j = 0; j < rows; j++) {
// Where are we, pixel-wise?
int x = i*cellSize;
int y = j*cellSize;
int loc = (video.width - x - 1) + y*video.width; // Reversing x to mirror the image
float r = red(video.pixels[loc]);
float g = green(video.pixels[loc]);
float b = blue(video.pixels[loc]);
// Make a new color with an alpha component
color c = color(r, g, b, 75);
// Code for drawing a single rect
// Using translate in order for rotation to work properly
pushMatrix();
translate(x+cellSize/2, y+cellSize/2);
// Rotation formula based on brightness
rotate((2 * PI * brightness(c) / 255.0));
rectMode(CENTER);
fill(c);
noStroke();
// Rects are larger than the cell for some overlap
rect(0, 0, cellSize+6, cellSize+6);
popMatrix();
}
}
}
}
I am interested to detect the movement to activate or desactivate this feature.
Please, Can you help me.
This is the error that I got:
The sketch path is not set. ==== JavaSound Minim Error ==== ==== java.lang.reflect.InvocationTargetException
=== Minim Error === === Couldn't load the file untitled.wav
Stack Overflow isn't really designed for general "how do I do this" type questions. It's for specific "I tried X, expected Y, but got Z instead" type questions. But I'll try to help in a general sense:
You need to break your problem down into smaller pieces and then take those pieces on one at a time. Get a simple example working. If you're asking about audio, then forget about the webcam for a second. Create a simple sketch that just plays a sound. Separately from that, create a simple sketch that just gets a webcam working. When you have those working perfectly, then you can think about combining them. But work your way forward in small steps. Write down exactly what you want to happen, in English, and that will be an algorithm that you can think about implementing with code.
Then if you get stuck, you can post a more specific question along with a MCVE. Good luck.
I want to add prefabs to my scene at random positions at runtime. However only one prefab is added to the screen and then I get the error Cannot cast from source type to destination type. This is what I'm trying now:
private void generateLevel() {
GameObject cube;
for (int i = 1; i < 9; i++) {
// Generate at random position in sphere
cube = (GameObject) Instantiate(prefabPlanet, Random.onUnitSphere, Quaternion.identity); // Error
// Random scale
cube.transform.localScale = new Vector3(1, 1, 1) * Random.Range(1f, 10f);
}
}
What could be the reason for this?
I found a solution which is to instantiate the GameObject without a variable, by modifying the prefab before the instantiation.
I'm not very happy with this solution though, since it might be useful to save the object in a variable.
for (int i = 1; i < 9; i++) {
// Random Scale
prefabPlanet.localScale = new Vector3(1, 1, 1) * Random.Range(1f, 10f);
// Random position
Vector3 position = Random.onUnitSphere * Constants.radius;
// Instatiate
Instantiate(prefabPlanet, position, Quaternion.identity);
}
This script works fine for me, I'm not sure what your doing wrong. Unless its erroring on the random scale part due to Constantes.maxScale having an illegitimate value. Ensure errors and warnings are turned on in your console and check it for errors on that line.
I am building a QT GUI application and use QImage for opening images.
My problem is that I can't figure out how to use QImage's bit() and scanline()
methods to get access at per pixel level.
I've seen this post Qt QImage pixel manipulation problems
but this is only for the first pixel of each row. Is this correct or I got it all wrong?
thanks in advance
The scanlines correspond to the the height of image, the columns correspond to the width of the image.
According to the docs, the prototype looks like uchar* QImage::scanline(int i), or a similar const version.
But, as a commenter pointed out, because the data is dependent on the machine architecture and image, you should NOT use the uchar * directly. Instead, use something like the following:
QRgb *rowData = (QRgb*)img.scanLine(row);
QRgb pixelData = rowData[col];
int red = qRed(pixelData);
It may not be immediately obvious from Kaleb's post, but the following works for setting a pixel on a Format_RGB32 image.
// Get the line we want
QRgb *line = (QRgb *)image->scanLine(row_index);
// Go to the pixel we want
line += col_index;
// Actually set the pixel
*line = qRgb(qRed(color), qGreen(color), qBlue(color));
The answer did not work for me. It looks like, the data is not 32bit aligned on my system.
To get the correct data, on my system i had to do this:
for(uint32_t Y = 0; Y < mHeight; ++Y)
{
uint8_t* pPixel = Image.scanLine(Y);
for(uint32_t X = 0; X < mWidth; ++X)
{
const int Blue = *pPixel++;
const int Green = *pPixel++;
const int Red = *pPixel++;
uint8_t GrayscalePixel = (0.21f * Red) + (0.72f * Green) + (0.07 * Blue);
}
}