C# - How to check if image is black/very dark

[OnlyOne]

Yes, i have GetPixelValue for

private NationalInstruments.CWIMAQControls.AxCWIMAQVision axCWIMAQVision1;

[Klemen]

Hello,

I am just guessing here, but this should then be an overloaded function. So if you have an 8-bit image, the prototype should look something like this:

uint8_t GetPixelValue(IMAQ image, int u, int v); // also incudes some error?

I just taking a guess here, since I don't have acces to Labview right now.

So you could probably do something like this:

double YOUR_FUNCTION(IMAQ image, int yT, int xL, int yB, int xR) {

uint8_t tmp;
unsigned long int sum = 0;
double average;

for(int j=yT;j<=yB;j++) {
    for(int i=xL;i<=xR;i++) {
       tmp = GetPixelValue(image,i,j);
       sum += (unsigned long int) tmp;
    }
}

average = (double) sum/(double)((xR-xL)*(yB-yT));
return average;
}

Where xL, xR, yT and yB are the top-left and bottom right coordinates of your ROI (mask).

This approach would be slower than pointer operation shown before.

I hope this helps in some way.

Best regards,

K

[Klemen]

Hello,

I was wrong, the function prototype looks like:

void  LV_GetPixelValue_v2(void *image, int32_t x, int32_t y, uint8_t *u8Pixel, uint16_t *u16Pixel, int16_t *i16Pixel, float *sglPixel, void *err);

So you would need to use the referenece operator (&):

uint8_t pixelValue;

.

.

.

void  LV_GetPixelValue_v2(void *image, int32_t x, int32_t y, &pixelValue, uint16_t *u16Pixel, int16_t *i16Pixel, float *sglPixel, void *err);

Best regards,

K

[muska]

I think counterpart for LabVIEW function "IMAQ Quantify" is in .NET available.

• QuantifyReport
  
  public sealed class QuantifyReport
      Member of NationalInstruments.Vision.Analysis
  
  Summary:
  A collection of NationalInstruments.Vision.Analysis.QuantifyReportItem objects. It contains one item for each region supplied to the NationalInstruments.Vision.Analysis.Algorithms.Quantify(NationalInstruments.Vision.VisionImage) method.
  
  
  I don't know how to use it. Is there any example?