Integral Histogram Errors

ali_mi

in Contributed Library Questions • 1 year ago

I have installed the IntegralHistogram library by Giovanni Tarducci and Alessio Barducci (Info here: http://inthistogram.altervista.org) and successfully ran the example "Image_ImgOutput" which writes the results into an output image.

However, when I try to run "Image_FileOutput", which as far as I understand, is supposed to write the results in an XML file, the program stops at the following line with a NullPointerException:

test.imageSearch(targetImg);

The full code of the example can be found here: http://inthistogram.altervista.org/examples/Image_FileOutput/Image_FileOutput.pde

The error message displayed in the console is as follows:

an error occurred while attempting to open the file

Exception in thread "Animation Thread" java.lang.NullPointerException

at integralhistogram.XMLSearchOut.startOutput(Unknown Source)

at integralhistogram.TargetUser.startOutput(Unknown Source)

at integralhistogram.IntHistUser.imageSearch(Unknown Source)

at integralhistogram_test1b.setup(integralhistogram_test1b.java:37)

at processing.core.PApplet.handleDraw(PApplet.java:1608)

at processing.core.PApplet.run(PApplet.java:1530)

at java.lang.Thread.run(Thread.java:680)

I am running Processing 1.5.1 on Mac OSX Lion. Any help would be appreciated on running this library properly.

Replies(5)

PhiLho

Re: Integral Histogram Errors

1 year ago

Is the path where it tries to write writable? Is the file name valid?

ali_mi

Re: Integral Histogram Errors

1 year ago

The path is relative, consisting only of a file name, so I assume it's the sketch folder. The file resides in the sketch folder.

At first when I ran the example as it is, I also thought that could have been caused by the file not existing (since I didn't know if the setOutputFile() function creates a file or not), so I created the file inside the sketch folder and re-ran the code, but no luck. It's the same error as running the original example code. For reference here's the code, with only one line modified from the original:

import integralhistogram.*;
void setup()
{
int bit = 2;
PImage imgSource = loadImage("image.png");
PImage imgTarg = loadImage("template.png");
TargetUser targetImg = new MyTargetUser(imgTarg,bit,2,0.022);
targetImg.setOutputFile("test.xml");
targetImg.startOutputFile();
IntHistUser test = new MyIntHistUser(imgSource,bit);
test.imageSearch(targetImg);
targetImg.endOutputFile();
println("File saved.");
}

PhiLho

Re: Integral Histogram Errors

1 year ago

I have no idea what is going on, as I don't know the library, but perhaps you can try and put an absolute path to a writable file in the setOutputFile() call.

ali_mi

Re: Integral Histogram Errors

1 year ago

That made it, thanks! I wouldn't guess that a Processing library tries to write by default somewhere where it doesn't have permission! This actually doesn't need an existing file, but can create a new file (also appends the .xml extension by itself) if the full path of the sketch folder is specified, such as this:

targetImg.setOutputFile("/Users/macbook/Documents/Processing/integralhistogram_test1b/out00");

PhiLho

Re: Integral Histogram Errors

1 year ago

Alternatively, you can use: targetImg.setOutputFile(sketchPath("out00"));

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