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Add clamp and scale_exp functions
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@nyalldawson
nyalldawson committed May 13, 2013
1 parent db619ed commit 10acbe0
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19 changes: 19 additions & 0 deletions resources/function_help/clamp-en_US
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<h3>clamp() function</h3>
Restricts an input value to a specified range.

<p><h4>Syntax</h4>
clamp(<i>minimum</i>,<i>input</i>,<i>maximum</i>)</p>

<p><h4>Arguments</h4>
<!-- List args for functions here-->
<i> minimum</i> &rarr; The smallest value <i>input</i> is allowed to take.<br>
<i> input</i> &rarr; a value which will be restricted to the range specified by <i>minimum</i> and <i>maximum</i>.<br>
<i> maximum</i> &rarr; The largest value <i>input</i> is allowed to take.<br>

<h4>Example</h4>
<!-- Show example of function.-->
clamp(1,5,10) &rarr; 5 (<i>input</i> is between 1 and 10 so is returned unchanged)<br>
clamp(1,0,10) &rarr; 1 (<i>input</i> is less than minimum value of 1, so function returns 1)<br>
clamp(1,11,10) &rarr; 10 (<i>input</i> is greater than maximum value of 10, so function returns 11)<br>


28 changes: 28 additions & 0 deletions resources/function_help/scale_exp-en_US
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<h3>scale_exp() function</h3>
Transforms a given value from an input domain to an output range using an exponential curve. This function can be used to ease values in or out
of the specified output range.

<p><h4>Syntax</h4>
scale_exp(<i>val</i>,<i>domain_min</i>,<i>domain_max</i>,<i>range_min</i>,<i>range_max</i>,<i>exponent</i>)</p>

<p><h4>Arguments</h4>
<!-- List args for functions here-->
<i> val</i> &rarr; is a value in the input domain. The function will return a corresponding scaled value in the output range.<br>
<i> domain_min, domain_max</i> &rarr; specify the input domain, the smallest and largest values the input <i>val</i> should take.<br>
<i> range_min, range_max</i> &rarr; specify the output range, the smallest and largest values which should be output by the function.<br>
<i> exponent</i> &rarr; a positive value (greater than 0), which dictates the way input values are mapped to the output range. Large exponents will cause the output values to 'ease in', starting slowly before
accelerating as the input values approach the domain maximum. Smaller exponents (less than 1) will cause output values to 'ease out', where the mapping starts quickly but slows as it approaches the domain maximum.<br>

<h4>Example</h4>
<!-- Show example of function.-->
<b>Easing in, using an exponent of 2:</b><br>
scale_exp(5,0,10,0,100,2) &rarr; 25<br>
scale_exp(7.5,0,10,0,100,2) &rarr; 56.25<br>
scale_exp(9.5,0,10,0,100,2) &rarr; 90.25<br>
<br>
<b>Easing out, using an exponent of 0.5:</b><br>
scale_exp(3,0,10,0,100,0.5) &rarr; 54.772<br>
scale_exp(6,0,10,0,100,0.5) &rarr; 77.459<br>
scale_exp(9,0,10,0,100,0.5) &rarr; 94.868<br>


87 changes: 75 additions & 12 deletions src/core/qgsexpression.cpp
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Expand Up @@ -442,29 +442,69 @@ static QVariant fcnRnd( const QVariantList& values, QgsFeature* , QgsExpression*
static QVariant fcnLinearScale( const QVariantList& values, QgsFeature* , QgsExpression* parent )
{
double val = getDoubleValue( values.at( 0 ), parent );
double domain_min = getDoubleValue( values.at( 1 ), parent );
double domain_max = getDoubleValue( values.at( 2 ), parent );
double range_min = getDoubleValue( values.at( 3 ), parent );
double range_max = getDoubleValue( values.at( 4 ), parent );
double domainMin = getDoubleValue( values.at( 1 ), parent );
double domainMax = getDoubleValue( values.at( 2 ), parent );
double rangeMin = getDoubleValue( values.at( 3 ), parent );
double rangeMax = getDoubleValue( values.at( 4 ), parent );

if ( domainMin >= domainMax )
{
parent->setEvalErrorString( QObject::tr( "Domain max must be greater than domain min" ) );
return QVariant();
}

// outside of domain?
if ( val >= domain_max )
if ( val >= domainMax )
{
return range_max;
return rangeMax;
}
else if ( val <= domain_min )
else if ( val <= domainMin )
{
return range_min;
return rangeMin;
}

// calculate linear scale
double m = ( range_max - range_min ) / ( domain_max - domain_min );
double c = range_min - ( domain_min * m );
double m = ( rangeMax - rangeMin ) / ( domainMax - domainMin );
double c = rangeMin - ( domainMin * m );

// Return linearly scaled value
return QVariant( m * val + c );
}

static QVariant fcnExpScale( const QVariantList& values, QgsFeature* , QgsExpression* parent )
{
double val = getDoubleValue( values.at( 0 ), parent );
double domainMin = getDoubleValue( values.at( 1 ), parent );
double domainMax = getDoubleValue( values.at( 2 ), parent );
double rangeMin = getDoubleValue( values.at( 3 ), parent );
double rangeMax = getDoubleValue( values.at( 4 ), parent );
double exponent = getDoubleValue( values.at( 5 ), parent );

if ( domainMin >= domainMax )
{
parent->setEvalErrorString( QObject::tr( "Domain max must be greater than domain min" ) );
return QVariant();
}
if ( exponent <= 0 )
{
parent->setEvalErrorString( QObject::tr( "Exponent must be greater than 0" ) );
return QVariant();
}

// outside of domain?
if ( val >= domainMax )
{
return rangeMax;
}
else if ( val <= domainMin )
{
return rangeMin;
}

// Return exponentially scaled value
return QVariant((( rangeMax - rangeMin ) / pow( domainMax - domainMin, exponent ) ) * pow( val - domainMin, exponent ) + rangeMin );
}

static QVariant fcnMax( const QVariantList& values, QgsFeature* , QgsExpression *parent )
{
//initially set max as first value
Expand Down Expand Up @@ -501,6 +541,27 @@ static QVariant fcnMin( const QVariantList& values, QgsFeature* , QgsExpression
return QVariant( minVal );
}

static QVariant fcnClamp( const QVariantList& values, QgsFeature* , QgsExpression* parent )
{
double minValue = getDoubleValue( values.at( 0 ), parent );
double testValue = getDoubleValue( values.at( 1 ), parent );
double maxValue = getDoubleValue( values.at( 2 ), parent );

// force testValue to sit inside the range specified by the min and max value
if ( testValue <= minValue )
{
return QVariant( minValue );
}
else if ( testValue >= maxValue )
{
return QVariant( maxValue );
}
else
{
return QVariant( testValue );
}
}

static QVariant fcnFloor( const QVariantList& values, QgsFeature* , QgsExpression* parent )
{
double x = getDoubleValue( values.at( 0 ), parent );
Expand Down Expand Up @@ -1342,8 +1403,8 @@ const QStringList &QgsExpression::BuiltinFunctions()
<< "abs" << "sqrt" << "cos" << "sin" << "tan"
<< "asin" << "acos" << "atan" << "atan2"
<< "exp" << "ln" << "log10" << "log"
<< "round" << "rand" << "randf" << "max" << "min"
<< "scale_linear" << "floor" << "ceil"
<< "round" << "rand" << "randf" << "max" << "min" << "clamp"
<< "scale_linear" << "scale_exp" << "floor" << "ceil"
<< "toint" << "toreal" << "tostring"
<< "todatetime" << "todate" << "totime" << "tointerval"
<< "coalesce" << "regexp_match" << "$now" << "age" << "year"
Expand Down Expand Up @@ -1389,7 +1450,9 @@ const QList<QgsExpression::Function*> &QgsExpression::Functions()
<< new StaticFunction( "randf", 2, fcnRndF, QObject::tr( "Math" ) )
<< new StaticFunction( "max", -1, fcnMax, QObject::tr( "Math" ) )
<< new StaticFunction( "min", -1, fcnMin, QObject::tr( "Math" ) )
<< new StaticFunction( "clamp", 3, fcnClamp, QObject::tr( "Math" ) )
<< new StaticFunction( "scale_linear", 5, fcnLinearScale, QObject::tr( "Math" ) )
<< new StaticFunction( "scale_exp", 6, fcnExpScale, QObject::tr( "Math" ) )
<< new StaticFunction( "floor", 1, fcnFloor, QObject::tr( "Math" ) )
<< new StaticFunction( "ceil", 1, fcnCeil, QObject::tr( "Math" ) )
<< new StaticFunction( "$pi", 0, fcnPi, QObject::tr( "Math" ) )
Expand Down
10 changes: 10 additions & 0 deletions tests/src/core/testqgsexpression.cpp
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Expand Up @@ -260,6 +260,9 @@ class TestQgsExpression: public QObject
QTest::newRow( "max(1,3.5,-2.1)" ) << "max(1,3.5,-2.1)" << false << QVariant( 3.5 );
QTest::newRow( "min(-1.5)" ) << "min(-1.5)" << false << QVariant( -1.5 );
QTest::newRow( "min(-16.6,3.5,-2.1)" ) << "min(-16.6,3.5,-2.1)" << false << QVariant( -16.6 );
QTest::newRow( "clamp(-2,1,5)" ) << "clamp(-2,1,5)" << false << QVariant( 1.0 );
QTest::newRow( "clamp(-2,-10,5)" ) << "clamp(-2,-10,5)" << false << QVariant( -2.0 );
QTest::newRow( "clamp(-2,100,5)" ) << "clamp(-2,100,5)" << false << QVariant( 5.0 );
QTest::newRow( "floor(4.9)" ) << "floor(4.9)" << false << QVariant( 4. );
QTest::newRow( "floor(-4.9)" ) << "floor(-4.9)" << false << QVariant( -5. );
QTest::newRow( "ceil(4.9)" ) << "ceil(4.9)" << false << QVariant( 5. );
Expand All @@ -271,6 +274,13 @@ class TestQgsExpression: public QObject
QTest::newRow( "scale_linear(-1,0,10,100,200)" ) << "scale_linear(-1,0,10,100,200)" << false << QVariant( 100. );
QTest::newRow( "scale_linear(11,0,10,100,200)" ) << "scale_linear(11,0,10,100,200)" << false << QVariant( 200. );

QTest::newRow( "scale_exp(0.5,0,1,0,1,2)" ) << "scale_exp(0.5,0,1,0,1,2)" << false << QVariant( 0.25 );
QTest::newRow( "scale_exp(0,0,10,100,200,2)" ) << "scale_exp(0,0,10,100,200,2)" << false << QVariant( 100. );
QTest::newRow( "scale_exp(5,0,10,100,200,2)" ) << "scale_exp(5,0,10,100,200,2)" << false << QVariant( 125. );
QTest::newRow( "scale_exp(10,0,10,100,200,0.5)" ) << "scale_exp(10,0,10,100,200,0.5)" << false << QVariant( 200. );
QTest::newRow( "scale_exp(-1,0,10,100,200,0.5)" ) << "scale_exp(-1,0,10,100,200,0.5)" << false << QVariant( 100. );
QTest::newRow( "scale_exp(4,0,9,0,90,0.5)" ) << "scale_exp(4,0,9,0,90,0.5)" << false << QVariant( 60. );

// cast functions
QTest::newRow( "double to int" ) << "toint(3.2)" << false << QVariant( 3 );
QTest::newRow( "text to int" ) << "toint('53')" << false << QVariant( 53 );
Expand Down

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