Code Snippet - Golden Template using TwinCAT Vision

What is a code snippet? These are mini blocks of code which help me to remember and reuse parts of Infosys.
These are not "Wow" level examples. They are just ultra simple, copy paste code. But as always, I like to share.

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Overview

The Golden Template code is a set of image processing steps that compares a "test image" to a "template image" and produces a score that is the sum of the number of non-zero pixels in two binary images.

This code can be useful for tasks such as image matching, object recognition, and pattern recognition.

Screenshot

Code Snippets

Only code related to Golden Template is included below. For the full code example please see the TwinCAT project.

PROGRAM MAIN
VAR
	// settings
	positiveThreshold : LREAL := 10;
	negativeThreshold : LREAL := -10;

	// variables
	readTestImage: FB_VN_ReadImage;
	readTemplateImage: FB_VN_ReadImage;
	result : HRESULT := S_OK;
	testImage : ITcVnImage;
	templateImage : ITcVnImage;
	testImageAsMonochrome : ITcVnImage;
	templateAsMonochrome : ITcVnImage;
	testImageAsMonochromeSigned16 : ITcVnImage;
	templateImageAsMonochromeSigned16 : ITcVnImage;
	subtractedImage : ITcVnImage;
	positiveThresholdImage : ITcVnImage;
	negativeThresholdImage : ITcVnImage;
	positiveThresholdImageUSINT : ITcVnImage;
	negativeThresholdImageUSINT : ITcVnImage;
	positiveScore : ULINT;
	negativeScore : ULINT;
	score : ULINT;
END_VAR

readTestImage(
    sFilePath   :=  'C:\temp\quality-image.png',
    ipDestImage :=  testImage,
    bRead       :=  TRUE,
    nTimeout    :=  T#5S
);

readTemplateImage(
    sFilePath   :=  'C:\temp\quality-template.png',
    ipDestImage :=  templateImage,
    bRead       :=  TRUE,
    nTimeout    :=  T#5S
);

IF readTestImage.bBusy OR readTestImage.bError OR testImage = 0 THEN
    RETURN;
END_IF

IF readTemplateImage.bBusy OR readTemplateImage.bError OR templateImage = 0 THEN
    RETURN;
END_IF

result := F_VN_ConvertColorSpace(testImage,testImageAsMonochrome,TCVN_CST_RGB_TO_GRAY,result);
result := F_VN_ConvertColorSpace(templateImage,templateAsMonochrome,TCVN_CST_RGB_TO_GRAY,result);
result := F_VN_ConvertElementType(testImageAsMonochrome,testImageAsMonochromeSigned16,TCVN_ET_INT,result);
result := F_VN_ConvertElementType(templateAsMonochrome,templateImageAsMonochromeSigned16,TCVN_ET_INT,result);
result := F_VN_SubtractImages(testImageAsMonochromeSigned16,templateImageAsMonochromeSigned16,subtractedImage,result);
result := F_VN_Threshold(subtractedImage,positiveThresholdImage,positiveThreshold,255,TCVN_TT_BINARY,result);
result := F_VN_Threshold(subtractedImage,negativeThresholdImage,negativeThreshold,255,TCVN_TT_BINARY_INV,result);
result := F_VN_ConvertElementType(positiveThresholdImage,positiveThresholdImageUSINT,TCVN_ET_USINT,result);
result := F_VN_ConvertElementType(negativeThresholdImage,negativeThresholdImageUSINT,TCVN_ET_USINT,result);
result := F_VN_CountNonZeroPixels(positiveThresholdImageUSINT,positiveScore,result);
result := F_VN_CountNonZeroPixels(negativeThresholdImageUSINT,negativeScore,result);

// low score = good match, high score = bad match
score := positiveScore + negativeScore;

Versions

• TcXaeShell 3.1.4024.35
• TwinCAT Vision 4.0.3.5

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