ColorMap::SetMap($aMap, $aInvert=false)

This is a polymorphic method that can take either a symbolic constant as argument and in that case specifies one of the built in color maps or it can be an array of colors which in that case specifies a manual color map. There are several built in color maps of different types which are referenced by an integer in range [0, 19]. A list of the built in color maps can be found in Section 22.8

For example the specification

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$mp->colormap->SetMap(0);

will make the library use the heat color map which is standard color map that goes from black for the min value up through red, orange, yellow and finally white for the highest value. This could be though of as the color of a heated iron rod (the hottest iron is white glowing).

The following manual specification uses three color plateau that the map touches.

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$map = array( 'navy', 'gray', 'red' );
$mp->colormap->Set($map);

would create a color map that would use 'navy' color for the min value and 'red' for the max value and linearly interpolate all other values for a color range continuously moving from 'navy'-'gray'-'red'. The color interpolation made between these values is a linear interpolation of the corresponding RGB values which creates the illusion of a continuous color change. The array must have at least two colors. There is no limit on the maximum number of base colors specified. However using more than ~7-10 colors to specify the color map is probably not to be recommended.

If $aInvert is set to true then the color map will be reversed so that the lowest color in the map will be the highest and vice versa.

ColorMap::GetCurrMap()

Return the current set color map

ClorMap::SetRange($aMin,$aMax)

This is used to manually specify the min and max values to be used for mapping matrix values to a color. Any values in the matrix that is lower than $aMin will be set to the min color and any values above $aMax will be set to the maximum color.

The matrix values in between will be mapped to the entire color scale. Another way of looking at this is that this will compress the dynamic range used or the colors. If the min and max values specified are much higher and lower than the actual content of the matrix the result is that most of the colors in the matrix will have "middle" colors (and hence lower the contrast). By default the values are (0,0) which means that the library will automatically determine the min/max value based on the input data and use the entire range of colors specified in the color map.

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<?php
// This will lower the contrast by roughly 50 percent 
$mindataval = ... ; // The minimum data value
$maxdataval = ... ; // The maximum data value
$contrast = -0.5;  // Reduce the contrast by 50%
$adj = ($maxdataval-$mindataval+1)*$contrast/2;
$matrixplot->colormap->SetRange($mindataval+$adj, $maxdataval-$adj);
?>

In a similar way the following code will instead increase the "contrast" 50% by letting a large part of the data values become mapped to the min and max color values.

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<?php
// This will increase the contrast by roughly 50 percent 
$mindataval = ... ; // The minimum data value
$maxdataval = ... ; // The maximum data value
$contrast = 0.5;  // Increase the contrast by 50%
$adj = ($maxdataval-$mindataval+1)*$contrast/2;
$matrixplot->colormap->SetRange($mindataval+$adj, $maxdataval-$adj);
?>

The three plots in Figure 22.3 shows the effect of increasing and decreasing the contrast with this method.

Figure 22.3. The effects of changing the value range for the colormap

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$matrixplot->SetAutoContrast(-0.3);

ColorMap::SetNumColors($aNum)

This is used to specify the number of discrete color steps used in the map. By default the scale range is divided in approximately 64 color buckets that all matrix entries are mapped into. Depending on the actual color map the specified value might be adjusted up or down up to +/- (p-1). Where p=number of base colors. Valid ranges are 3-128 but is also dependent on the actual color map.

The reasons for these restriction and the adjustments are

ColorMap::SetNullColor($aColor)

If specified this determines what color will be used for any values in the matrix that are null

MatrixPlot::SetModuleType($aType)

$aType, 0 = Use rectangle, 1 = Use a circle

MatrixPlot::SetBackgroundColor($aColor)

MatrixPlot::SetAlpha($aAlpha)

$aAlpha , 0=No transparency, 1=Full transparency (not so useful since then only the background can be seen)

MatrixPlot::SetSize($aW,$aH)

MatrixPlot::SetSize($aW)

If the two arguments are numbers in range [0.0, 1.0] it will be interpreted as specifying the size as fractions of the overall graph width and height. If the number are > 1 they will be interpreted as the absolute size (in pixels). It is perfectly possible to mix teh two ways. For example the following is a valid size specification

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$matrixplot->SetSize(250,0.6); // 250px wide and height will be ~60% of the graph height

If only one argument is specified it will set both the width and height to the specified size. If the single size is specified as a fraction the smallest of the graph width/height will be used as the base.

MatrixPlot::SetModuleSize($aW,$aH)

The two argument specifies the module size, i.e. the size of each cell in the plot (in pixels).

MatrixPlot::SetCenterPos($aX,$aY)

Specifies the center of the plot to be the given x and y-coordinates. The position can be specified in either absolute pixels or as fractions of the width and height (or as a combination).

MatrixPlot::legend

MatrixPlot::SetLegendLayout($aPos)

The position of the legend is specified as an integer in range [0-3] where 0 is the right side of the plot and the remaining posiotins follow clockwise from the right, (i.e. 1 is the bottom, 2 is the left and 3 is the top side).

MatrixLegend::Show($aFlg=true)

Used to enable/disable the legend. The following code line would hide the legend

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$matrixplot->legend->Show(false);

MatrixLegend::SetModuleSize($aBucketWidth,$aBucketHeight=5)

This specifies the size of each color bucket in the legend.

MatrixLegend::SetSize($aWidth,$aHeight=5)

This is an alternative way to specify the size of the legend compare with the individual bucket specification. With this method the overall width and height of the legend bar can be adjusted. The size can be specified s either absolute pixels or as fraction of the width height of the entire graph.

MatrixLegend::SetMargin($aMargin)

Specifies the margin (in pixels) between the matrix plot and the legend.

MatrixLegend::SetLabelMargin($aMargin)

Specifies the margin between the min/max label and the legend bar

MatrixLegend::SetFont($aFamily,$aStyle,$aSize)

Specifies the font for the label on the legend

MatrixLegend::SetFormatString($aStr)

Specifies the format string (in printf() format) to be used when rendering the legend label

MatrixPlot::collabel

Instance for horizontal labels

MatrixPlot::rowlabel

Instance for vertical labels

EdgeLabel::SetFont($aFF,$aFS,$aSize)

Specify the font to be used. Keep in mind that the font size should not be larger than the module size chosen to be able to fit within the row/column it specifies. For the default module size a font size of 8-9 for a TTF font is usually fine. By default the labels are set in FF_ARIAL, 8 pt size.

EdgeLabel::SetFontColor($aColor)

Specifies the font color.

EdgeLabel::SetMargin($aMargin)

Set the margin from the edge of the matrix in pixels.

EdgeLabel::SetSide($aSide)

Specifies on what side the labels should be drawn. For horizontal (x) labels the possible sides are "left" or "right" and for vertical (y) the possible sides are "top" and "bottom".

EdgeLabel::Set($aLabels)

Specifies the 1-dimensional array that holds the labels to be used.

EdgeLabel::SetAngle($aAngle)

Specify the angle to draw the label at. By default row labels are drawn at 0 degree and column labels are drawn at 90 degrees angle.