Blobscanner - The operator != is undefined for the argument type(s) float, null

PhiLho

Re: Blobscanner - The operator != is undefined for the argument type(s) float, null

2 years ago

Strange error. It appears that bd.getCentroidX(blobID) is returning a float.So, indeed, you cannot test it against null, a primitive value can never be null.
Now, if you get an NPE on this expression, it can only be because bd is null. So the correct test is if (bd != null) {

clankill3r

Re: Blobscanner - The operator != is undefined for the argument type(s) float, null

2 years ago

No it does not work :(

the println is Blobscanner.Detector@c4bc34

I think it's a library bug, if you think else plz let me know.

For now i will contact the creator.

O damn i'm dead...

if(bd != null) {
println(bd);
//if(bd.getCentroidX(blobID) != null) {
point(bd.getCentroidX(blobID), bd.getCentroidY(blobID));
}

PhiLho

Re: Blobscanner - The operator != is undefined for the argument type(s) float, null

2 years ago

Well, you should look at the doc. We don't know what is bd (apparently a Blobscanner object) nor what getCentroidX() is supposed to return (here it looks like a Detector?). We are reduced to guesses based on your vague error messages.
Beside, if bd is null, you should not call point() with it.

clankill3r

Re: Blobscanner - The operator != is undefined for the argument type(s) float, null

2 years ago

I did look at the doc, but it doesn't help.

bd is a class, detector, created by:

Detector(processing.core.PApplet p5, int sx, int sy, int w, int h, int threshold)

getCentroidX:

float getCentroidX(int blobnumber)
Returns the blob centroid x coordinate.

I think the library does something very strange.

In case you want to try,

last post (atm):

http://forum.processing.org/topic/new-blob-detection-and-analysis-image-labelling-and-segmentation-library-for-processing

p.s. it only writes a point if it's not null.

PhiLho

Re: Blobscanner - The operator != is undefined for the argument type(s) float, null

2 years ago

I paid no attention you changed the println() from the first post. So getCentroidX actually returns a float.
I don't see where the problem is, then.
The Detector class just didn't get a proper toString() method, so Java displays its class name and id. That's all.

clankill3r

Re: Blobscanner - The operator != is undefined for the argument type(s) float, null

2 years ago

getCentroidX returns a float in theorie.

the void detectBlob is inside a class called Rotor.

blobID is -1, so it means it's not set, every frame it will be reset to -1.

In the for loop it searches for the biggest blob and stores the blob numer of it.

After that i want the x and y of that blob but it always leaves me with a nullPointerException.

but it's just a bug in the library...

void detectBlob() {
bd.imageFindBlobs(checkArea);
bd.loadBlobsFeatures();// to call always before to use a method returning or processing a blob feature
bd.weightBlobs(true);
//println(bd.getBlobsNumber() + " BLOBS FOUND");
int maxBlobWeight = MIN_INT;
int blobID = -1;
for(int i = 0; i < bd.getBlobsNumber(); i++) {
int weight = bd.getBlobWeight(i);
if (weight > maxBlobWeight) maxBlobWeight = weight;
blobID = i;
}
//println(bd.getCentroidX(blobID));
if(bd != null) {
println(bd);
println(blobID);
//if(bd.getCentroidX(blobID) != null) {
//println(maxBlobWeight);
point(bd.getCentroidX(blobID), bd.getCentroidY(blobID));
}
}

PhiLho

Re: Blobscanner - The operator != is undefined for the argument type(s) float, null

2 years ago

blobID is -1 because bd.getBlobsNumber() returns 0, probably. Nothing is detected.

clankill3r

Re: Blobscanner - The operator != is undefined for the argument type(s) float, null

2 years ago

blodID is a value i made, and i have set it to -1.

If i println it it is not -1 so something must have been found.

So something is detected, and if it didn't detect anything then it should still be possible to not have processing stop on a NPE.

thanks anyway

robdanet

Re: Re: Blobscanner - The operator != is undefined for the argument type(s) float, null

2 years ago

Hi I checked your code and the bug is there : before call getCentroidX(int forblobnumber) or
getCentroidY(int forblobnumber) you need call findCentroids(boolean printCentroidsValue, boolean drawThem). Also , if you only need the centroids value to draw them you can just write :

strokeWeight(your favourite stroke weight);
stroke(you favourite color);
bd.findCentroids(false, true);//if both true, it will print also the value to the console output

Do not forget that calling these methods implies a call on the same instance and for each instance to l oadBlobsFeatures() method. The javadoc explain this particular thing quite well for all the methods (though, in the current version I didn’t update the findCentroids method comment, so they still show it getting one Boolean argument, not two) .

Two more thing, getCentroidX returns a float so it can’t be null,but you can write if(Boolean((int)float value))
more simply > 0.0 .
I had to rewrite the code because I cant use processing.video library with my camera in the last release of Processing , but if you need it, let me know your email and I will send it to you. Please send me a copy of the project once it is finished or a video, I will post it on the project's blog.

5* for the code
1* for not reading javadoc well enough

tony

" It is more blessed to give than to receive"
- Jesus of Nazareth

robdanet

Re: Blobscanner - The operator != is undefined for the argument type(s) float, null

2 years ago

Hi

I went to check the javadoc in the zip and I realized they were for the second release. I have just uploaded a new version with the correct javadoc. Thanks for having got the issue out, I RETIRE THE 1* !

tony

" It is more blessed to give than to receive"
- Jesus of Nazareth

clankill3r

Re: Blobscanner - The operator != is undefined for the argument type(s) float, null

2 years ago

you and phi.lho are god in human form!

thanks, i go check it now

clankill3r

Re: Blobscanner - The operator != is undefined for the argument type(s) float, null

2 years ago

yeah :)

good to know that the next problems i run into have nothing to do with the blobscanner :)

p.s. it would be nice if blobscanner allows to change the threshold value.

robdanet

Re: Blobscanner - The operator != is undefined for the argument type(s) float, null

2 years ago

It will, but I can share a foretaste on this one.

// A variable threshold filter class
// Antonio Molinaro 27/02/2011
VariableThreshold vt;
PImage source;
PImage destination;
float threshold;
void setup() {
size(200,200);
source = loadImage( "image.jpg" );
vt = new VariableThreshold();
}
void draw() {
image(vt.getImage(source),0,0);
}
void mouseDragged(){
vt.setThreshold((float)mouseX,0.0,200.0,0.0,255.0);
println(vt.getThreshold());
}
void mousePressed(){
vt.setThreshold(random(255));
println(vt.getThreshold());
}
//==========================
// variable threshold class
// @autor Antonio Molinaro
// @date 13/09/2009
//==========================
class VariableThreshold {
PImage dst;
float threshold;
public VariableThreshold(){}
/**
* Sets a fixed threshold value
* @param T thre threshold to apply
*/
public void setThreshold(float T){
threshold = T;
}
/**
* Sets a variable threshold value
* @param controlValue The control variable value
* @param controlValueMin The control variable max value
* @param controlValueMax The control variable min value
* @param from_T The Threshold min value
* @param to_T The threshold max value
*/
public void setThreshold(float controlValue,
float controlValueMin,
float controlValueMax,
float from_T,
float to_T){
threshold = map(controlValue,controlValueMin, controlValueMax, from_T, to_T);
}
/**
* Applies the variable threshold filter
* to the src PImage parameter
* @param src Thre PImage to filter
* @return a PImage object
* representing the filtered PImage passed
* as argument to the mothod
*/
public PImage getImage(PImage src){
dst = createImage(src.width, src.height, 12);
src.loadPixels();
dst.loadPixels();
for (int x = 0; x < src.width; x++ ) {
for (int y = 0; y < src.height; y++ ) {
int loc = x + y * src.width;
if (brightness(src.pixels[loc]) > threshold){
dst.pixels[loc] = color(255);
} else {
dst.pixels[loc] = color(0);
}
}
}
dst.updatePixels();
return dst;
}
/**
* Returns the threshold value used by the filter
*/
public float getThreshold(){
return threshold;
}
}

" It is more blessed to give than to receive"
- Jesus of Nazareth