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Canny edge detector: Difference between revisions
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There is a built-in function, [http://www.mathworks.com/help/images/ref/edge.html edge], that has Canny Edge Detection as one of its options.
<lang MATLAB>BWImage = edge(GrayscaleImage,'canny');</lang>
=={{header|PHP}}==
PHP implementation
<lang PHP>
// input: r,g,b in range 0..255
function RGBtoHSV($r, $g, $b) {
$r = $r/255.; // convert to range 0..1
$g = $g/255.;
$b = $b/255.;
$cols = array("r" => $r, "g" => $g, "b" => $b);
asort($cols, SORT_NUMERIC);
$min = key(array_slice($cols, 1)); // "r", "g" or "b"
$max = key(array_slice($cols, -1)); // "r", "g" or "b"
// hue
if($cols[$min] == $cols[$max]) {
$h = 0;
} else {
if($max == "r") {
$h = 60. * ( 0 + ( ($cols["g"]-$cols["b"]) / ($cols[$max]-$cols[$min]) ) );
} elseif ($max == "g") {
$h = 60. * ( 2 + ( ($cols["b"]-$cols["r"]) / ($cols[$max]-$cols[$min]) ) );
} elseif ($max == "b") {
$h = 60. * ( 4 + ( ($cols["r"]-$cols["g"]) / ($cols[$max]-$cols[$min]) ) );
}
if($h < 0) {
$h += 360;
}
}
// saturation
if($cols[$max] == 0) {
$s = 0;
} else {
$s = ( ($cols[$max]-$cols[$min])/$cols[$max] );
$s = $s * 255;
}
// lightness
$v = $cols[$max];
$v = $v * 255;
return(array($h, $s, $v));
}
$filename = "image.png";
$dimensions = getimagesize($filename);
$w = $dimensions[0]; // width
$h = $dimensions[1]; // height
$im = imagecreatefrompng($filename);
for($hi=0; $hi < $h; $hi++) {
for($wi=0; $wi < $w; $wi++) {
$rgb = imagecolorat($im, $wi, $hi);
$r = ($rgb >> 16) & 0xFF;
$g = ($rgb >> 8) & 0xFF;
$b = $rgb & 0xFF;
$hsv = RGBtoHSV($r, $g, $b);
// compare pixel below with current pixel
$brgb = imagecolorat($im, $wi, $hi+1);
$br = ($brgb >> 16) & 0xFF;
$bg = ($brgb >> 8) & 0xFF;
$bb = $brgb & 0xFF;
$bhsv = RGBtoHSV($br, $bg, $bb);
// if difference in hue > 20, edge is detected
if($hsv[2]-$bhsv[2] > 20) {
imagesetpixel($im, $wi, $hi, imagecolorallocate($im, 255, 0, 0));
}
else {
imagesetpixel($im, $wi, $hi, imagecolorallocate($im, 0, 0, 0));
}
}
}
header('Content-Type: image/jpeg');
imagepng($im);
imagedestroy($im);
</lang>
=={{header|Phix}}==
{{improve|Phix|Port to pGUI for linux and 64 bit compatibility.}}
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