//finding position of patch in strings
$find = explode($image2,$image);
$coordinate = substr_count($find[0], '|');
//converting position from string to x y coordinates
$width = imagesx($im);
$check = $coordinate / $width;
$check = explode(".",$check);
$y = $check[0] + 1;
$x = $coordinate % $width;
if(($coordinate % $width) == 0)
{
$x = $width;
$y--;
}
//printing result
echo "x: {$x}<br>y: {$y}";
?>
I tested each individual component of that manually and they all worked, but when put together it doesn't find the proper coordinates, just bogus ones. If someone could shed some light on this I would really appreciate it
Dude, your algorithm needs some work. Instead of storing everything in a massive string like that and then using explode, try this:
Load up both your large and small images
Use a loop (two levels deep) to go through every pixel in your large image. If the pixel you are at in your large image matches the top left pixel of your small image, then step into a verify subroutine
The verify subroutine would then check the other pixels to see if they are a match. You could probably get away with checking a fairly low percentage of pixels - maybe check a grid with 10px in between each. This would depend on the desired size of your small image, but you should be able to get pretty good results (and much more efficiently)
// Small Image
$small = ImageCreateFromPNG("small.png");
// Loop over every pixel in the large image
for($cy = 0; $cy < $big_h; $cy++) { // This loops over vertically
for($cx = 0; $cx < $big_w; $cx++) { // This loops over horizontally
if(imagecolorat($big, $cx, $cy) == imagecolorat($small, 0, 0)) { // See if the current pixel in the large image matches the top left pixel in the small one
if(verify($cx, $cy, $big, $small)) { // If there is a potential match, verify if it is a full match
die("X=$cx, Y=$cy"); // If it is a full match, stop doing work and output the result
}
}
}
}
echo "Not Found"; // No match found
// Check and see if the given cx, cy position is a match
function verify($cx, $cy, &$big, &$small) { // The & passes by reference...basically just saves you memory
$small_w = imagesx($small);
$small_h = imagesy($small);
// Use the threshhold to prevent checking every single pixel. It can be assumed that if you
// have a spaced out grid of matches, you are pretty close
$threshhold = 20;
for($sy = 0; $sy < $small_h; $sy+=$threshhold) {
for($sx = 0; $sx < $small_w; $sx+=$threshhold) {
if(imagecolorat($small, $sx, $sy) != imagecolorat($big, $cx + $sx, $cy + $sy)) {
return false;
}
}
}
return true;
}
// Small Image
$small = ImageCreateFromPNG("small.png");
// Loop over every pixel in the large image
for($cy = 0; $cy < $big_h; $cy++) { // This loops over vertically
for($cx = 0; $cx < $big_w; $cx++) { // This loops over horizontally
if(imagecolorat($big, $cx, $cy) == imagecolorat($small, 0, 0)) { // See if the current pixel in the large image matches the top left pixel in the small one
if(verify($cx, $cy, $big, $small)) { // If there is a potential match, verify if it is a full match
die("X=$cx, Y=$cy"); // If it is a full match, stop doing work and output the result
}
}
}
}
echo "Not Found"; // No match found
// Check and see if the given cx, cy position is a match
function verify($cx, $cy, &$big, &$small) { // The & passes by reference...basically just saves you memory
$small_w = imagesx($small);
$small_h = imagesy($small);
// Use the threshhold to prevent checking every single pixel. It can be assumed that if you
// have a spaced out grid of matches, you are pretty close
$threshhold = 20;
for($sy = 0; $sy < $small_h; $sy+=$threshhold) {
for($sx = 0; $sx < $small_w; $sx+=$threshhold) {
if(imagecolorat($small, $sx, $sy) != imagecolorat($big, $cx + $sx, $cy + $sy)) {
return false;
}
}
}
return true;
}
?>
That works beautifully, thank you The only part I don't understand is in your for statement in the verify function where you put +=
Quote:
Originally Posted by bacterozoid
Dude, your algorithm needs some work. Instead of storing everything in a massive string like that and then using explode, try this:
Load up both your large and small images
Use a loop (two levels deep) to go through every pixel in your large image. If the pixel you are at in your large image matches the top left pixel of your small image, then step into a verify subroutine
The verify subroutine would then check the other pixels to see if they are a match. You could probably get away with checking a fairly low percentage of pixels - maybe check a grid with 10px in between each. This would depend on the desired size of your small image, but you should be able to get pretty good results (and much more efficiently)
Yep. This way you're not checking every single pixel - your script will complete quicker and use less resources.
Skipping every 20px (at least on an image this size) should generally be good enough to detect a match, as the likliehood of that happening anywhere else in the image is pretty low. If you have problems, just decrease that threshold value.
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