public static Image1f CreateGaussiankernel( float sigma )
{
float sigmaSquared = sigma * sigma;
float twoSigma = 2.0f * sigma;
int radius = twoSigma.CeilToInt();
int diameter = 2 * radius + 1;
Image1f kernel = new Image1f( diameter, diameter );
float sum = 0;
for( int y = 0; y < diameter; ++y )
{
int dy = y - radius;
for( int x = 0; x < diameter; ++x )
{
int dx = x - radius;
float val = ( float )( Math.Exp( -0.5f * ( dx * dx + dy * dy ) / sigmaSquared ) );
sum += val;
kernel[ x, y ] = val;
}
}
for( int y = 0; y < diameter; ++y )
{
for( int x = 0; x < diameter; ++x )
{
kernel[ x, y ] /= sum;
}
}
return kernel;
}
public void Apply( Image1f input, Image1f output )
{
float[,] controlPoints = new float[ 4, 4 ];
int w_out = output.Width;
int h_out = output.Height;
int w_in = input.Width;
int h_in = input.Height;
// scaling coefficients
float x_outToIn = Arithmetic.DivideIntsToFloat( w_in, w_out );
float y_outToIn = Arithmetic.DivideIntsToFloat( h_in, h_out );
for( int yOut = 0; yOut < h_out; ++yOut )
{
float yInFloat = ( yOut + 0.5f ) * y_outToIn;
int yIn0 = yInFloat.FloorToInt() - 1;
int yIn1 = yIn0 + 3;
for( int xOut = 0; xOut < w_out; ++xOut )
{
float xInFloat = ( xOut + 0.5f ) * x_outToIn;
int xIn0 = xInFloat.FloorToInt() - 1;
int xIn1 = xIn0 + 3;
// grab the 16 control points
for( int yc = yIn0; yc <= yIn1; ++yc )
{
int dy = yc - yIn0;
int ycc = Arithmetic.Clamp( yc, 0, h_in );
for( int xc = xIn0; xc <= xIn1; ++xc )
{
int dx = xc - xIn0;
int xcc = Arithmetic.Clamp( xc, 0, w_in );
controlPoints[ xc, yc ] = input[ xcc, ycc ];
}
}
// compute Catmull-Rom splines in the x direction
float tx = Arithmetic.FractionalPart( xInFloat );
float ty = Arithmetic.FractionalPart( yInFloat );
var v0i = EvaluateSpline( controlPoints[ 0, 0 ], controlPoints[ 0, 1 ], controlPoints[ 0, 2 ], controlPoints[ 0, 3 ], tx );
var v1i = EvaluateSpline( controlPoints[ 1, 0 ], controlPoints[ 1, 1 ], controlPoints[ 1, 2 ], controlPoints[ 1, 3 ], tx );
var v2i = EvaluateSpline( controlPoints[ 2, 0 ], controlPoints[ 2, 1 ], controlPoints[ 2, 2 ], controlPoints[ 2, 3 ], tx );
var v3i = EvaluateSpline( controlPoints[ 3, 0 ], controlPoints[ 3, 1 ], controlPoints[ 3, 2 ], controlPoints[ 3, 3 ], tx );
var vii = EvaluateSpline( v0i, v1i, v2i, v3i, ty );
output[ xOut, yOut ] = vii;
}
}
}
public static void Apply( Image1f input, Image1f output )
{
if( input.Size != output.Size )
{
throw new ArgumentException( "input and output must be of the same size" );
}
float min;
float max;
input.Pixels.MinMax( f => f, out min, out max );
float reciprocalRange = 1.0f / ( max - min );
for( int k = 0; k < input.NumPixels; ++k )
{
float vIn = input[ k ];
float vOut = ( vIn - min ) * reciprocalRange;
output[ k ] = vOut;
}
}
public static Vector2f SnapToEdge( Image1f gradientNorm, Vector2f p, int radius )
{
Vector2i q = p.RoundToInt();
float max = float.NegativeInfinity;
Vector2f maxQ = Vector2f.Zero;
for( int y = q.y - radius; y <= q.y + radius; ++y )
{
for( int x = q.x - radius; x <= q.x + radius; ++x )
{
float gn = gradientNorm[ x, y ];
if( gn > max )
{
max = gn;
maxQ = new Vector2f( x, y );
}
}
}
return maxQ;
}
public static void CopySubImage( Image1f source, int sx, int sy,
Image1f target, int tx, int ty,
int width, int height )
{
int sw = source.Width;
int sh = source.Height;
int tw = target.Width;
int th = target.Height;
if( sx < 0 || sy < 0 || sx >= sw || sy >= sh )
{
throw new IndexOutOfRangeException( "Source origin must be inside source image" );
}
if( tx < 0 || ty < 0 || tx >= tw || ty >= th )
{
throw new IndexOutOfRangeException( "Target origin must be inside target image" );
}
int tx0 = tx;
int tx1 = Math.Min( tx + width, tw );
int ty0 = ty;
int ty1 = Math.Min( ty + height, th );
for( int y = ty0; y < ty1; ++y )
{
int dy = y - ty0;
int iy = sy + dy.Clamp( 0, sh );
for( int x = tx0; x < tx1; ++x )
{
int dx = x - tx0;
int ix = ( sx + dx ).Clamp( 0, sw );
target[ x, y ] = source[ ix, iy ];
}
}
}
public static void Apply( Image1f input, Image1f output )
{
int w_out = output.Width;
int h_out = output.Height;
int w_in = input.Width;
int h_in = input.Height;
// scaling coefficients
float x_outToIn = Arithmetic.DivideIntsToFloat( w_in, w_out );
float y_outToIn = Arithmetic.DivideIntsToFloat( h_in, h_out );
for( int yOut = 0; yOut < h_out; ++yOut )
{
float yInFloat = ( yOut + 0.5f ) * y_outToIn;
for( int xOut = 0; xOut < w_out; ++xOut )
{
float xInFloat = ( xOut + 0.5f ) * x_outToIn;
output[ xOut, yOut ] = input.BilinearSample( xInFloat, yInFloat );
}
}
}