SVG Coordinate translation

Why doesn't this SVG inline code produce a box 60 by 40 with a dot in the middle?

I would like to plot items on a regular Cartesian coordinate map using 开发者_Python百科SVG. The data I would have would be the size of the displayable map and center point on the Cartesian main map.

<svg xmlns="http://www.w3.org/2000/svg" width="60" height="40" viewBox="0 0 60 40">
  <g transform="translate(-470,480) scale(1,-1)">
    <circle title="Center" cx="500" cy="500" r="3" fill="red"/>
  </g>
</svg>

Your code is creating an 60 by 40 pixel SVG, then:

• Draws a circle centred on (500, 500)
• The scale transform moves the circle to (500, -500)
• The translate transform moves it to (30, -20)

If you change the transform to transform="translate(-470,520) scale(1,-1)" you should get what I think you want.

I came up with this code snippet that will create a map of with Cartesian coordinates and plot them in an SVG window using those coordinates. Hope this will help somebody.

The function takes the center of the map as $x, $y and draws the map around that coordinate.

    public static function xyMap( $x, $y, $width = 0, $height = 0, $show = array('X')) {

    $minx = $x - ($width / 2);
    $maxx = $x + ($width / 2);

    if ($minx < 0) {
        $minx = 0;
        $maxx = $width;
    } elseif ($maxx > Yii::app()->params['maxMapX']) {
        $maxx = Yii::app()->params['maxMapX'];
        $minx = Yii::app()->params['maxMapX'] - $width;
    }

    $miny = $y - ($height / 2);
    $maxy = $y + ($height / 2);

    if ($miny < 0) {
        $miny = 0;
        $maxy = $height;
    } elseif ($maxy > Yii::app()->params['maxMapY']) {
        $maxy = Yii::app()->params['maxMapY'];
        $miny = Yii::app()->params['maxMapY'] - $height;
    }


    $x_xform = -1 * $minx;
    $y_xform = $maxy;

    $x_scale = 1;
    $y_scale = -1;

    echo "<svg xmlns=\"http://www.w3.org/2000/svg\" width=\"$width\" height=\"$height\" viewBox=\"0 0 $width $height\">\n";
    echo "<g transform=\"translate($x_xform, $y_xform) scale($x_scale,$y_scale)\">\n";
    echo "<rect x=\"$minx\" y=\"$miny\" width=\"$width\" height=\"$height\" stroke=\"black\" stroke-width=\"2\" fill=\"white\" />\n";
    echo "<circle title=\"Center\" cx=\"$x\" cy=\"$y\" r=\"3\" fill=\"red\"/>\n";
    echo "</g>\n</svg>\n";

}