我有两张照片（小的和大的）。其中一个包含另一个。一张图片是一张照片，另一张是这张照片所在相册页面的图片。我希望你明白我说的话。
那么，如何使用php获得大图像上小图像的坐标（x，y）？

最佳答案

不依赖外部lib而不是gd，自己做起来相当容易。
您需要注意的是，您很可能无法执行简单的逐像素检查，因为过滤和压缩可能会稍微修改每个像素的值。
我在这里提出的代码很可能是慢的，如果性能是一个问题，你可以优化它或采取捷径。希望代码能让你走上正轨！
首先，让我们重复我们的图片

$small = imagecreatefrompng("small.png");
$large = imagecreatefrompng("large.png");

$smallwidth = imagesx($small);
$smallheight = imagesy($small);

$largewidth = imagesx($large);
$largeheight = imagesy($large);

$foundX = -1;
$foundY = -1;

$keepThreshold = 20;

$potentialPositions = array();

for($x = 0; $x <= $largewidth - $smallwidth; ++$x)
{
    for($y = 0; $y <= $largeheight - $smallheight; ++$y)
    {
        // Scan the whole picture
        $error = GetImageErrorAt($large, $small, $x, $y);
        if($error["avg"] < $keepThreshold)
        {
            array_push($potentialPositions, array("x" => $x, "y" => $y, "error" => $error));
        }
    }
}

imagedestroy($small);
imagedestroy($large);

echo "Found " . count($potentialPositions) . " potential positions\n";

function GetImageErrorAt($haystack, $needle, $startX, $startY)
{
    $error = array("red" => 0, "green" => 0, "blue" => 0, "avg" => 0);
    $needleWidth = imagesx($needle);
    $needleHeight = imagesy($needle);

    for($x = 0; $x < $needleWidth; ++$x)
    {
        for($y = 0; $y < $needleHeight; ++$y)
        {
            $nrgb = imagecolorat($needle, $x, $y);
            $hrgb = imagecolorat($haystack, $x + $startX, $y + $startY);

            $nr = $nrgb & 0xFF;
            $hr = $hrgb & 0xFF;

            $error["red"] += abs($hr - $nr);

            $ng = ($nrgb >> 8) & 0xFF;
            $hg = ($hrgb >> 8) & 0xFF;

            $error["green"] += abs($hg - $ng);

            $nb = ($nrgb >> 16) & 0xFF;
            $hb = ($hrgb >> 16) & 0xFF;

            $error["blue"] += abs($hb - $nb);
        }
    }
    $error["avg"] = ($error["red"] + $error["green"] + $error["blue"]) / ($needleWidth * $needleHeight);
    return $error;
}

function SortOnAvgError($a, $b)
{
    if($a["error"]["avg"] == $b["error"]["avg"])
    {
        return 0;
    }
    return ($a["error"]["avg"] < $b["error"]["avg"]) ? -1 : 1;
}

if(count($potentialPositions) > 0)
{
    usort($potentialPositions, "SortOnAvgError");
    $mostLikely = $potentialPositions[0];
    echo "Most likely at " . $mostLikely["x"] . "," . $mostLikely["y"];
}

Found 5 potential positions
Most likely at 288,235

function microtime_float()
{
    list($usec, $sec) = explode(" ", microtime());
    return ((float)$usec + (float)$sec);
}

$time_start = microtime_float();

$time_end = microtime_float();
echo "in " . ($time_end - $time_start) . " seconds\n";

function GetImageErrorAt($haystack, $needle, $startX, $startY, $increment)
{
    $needleWidth = imagesx($needle);
    $needleHeight = imagesy($needle);

    $error = array("red" => 0, "green" => 0, "blue" => 0, "avg" => 0, "complete" => true);

    for($x = 0; $x < $needleWidth; $x = $x + $increment)
    {
        for($y = 0; $y < $needleHeight; $y = $y + $increment)
        {
            $hrgb = imagecolorat($haystack, $x + $startX, $y + $startY);
            $nrgb = imagecolorat($needle, $x, $y);

            $nr = $nrgb & 0xFF;
            $hr = $hrgb & 0xFF;

            $ng = ($nrgb >> 8) & 0xFF;
            $hg = ($hrgb >> 8) & 0xFF;

            $nb = ($nrgb >> 16) & 0xFF;
            $hb = ($hrgb >> 16) & 0xFF;

            $error["red"] += abs($hr - $nr);
            $error["green"] += abs($hg - $ng);
            $error["blue"] += abs($hb - $nb);
        }
    }

    $error["avg"] = ($error["red"] + $error["green"] + $error["blue"]) / ($needleWidth * $needleHeight);

    return $error;
}

$stepSize = 10;

for($x = 0; $x <= $largewidth - $smallwidth; $x = $x + $stepSize)
{
    for($y = 0; $y <= $largeheight - $smallheight; $y = $y + $stepSize)
    {
        // Scan the whole picture
        $error = GetImageErrorAt($large, $small, $x, $y, 2);
        if($error["complete"] == true && $error["avg"] < $keepThreshold)
        {
            array_push($potentialPositions, array("x" => $x, "y" => $y, "error" => $error));
        }
    }
}

Found 8 potential positions
Most likely at 290,240

if(count($potentialPositions) > 0)
{
    usort($potentialPositions, "SortOnAvgError");
    $mostLikely = $potentialPositions[0];
    echo "Most probably around " . $mostLikely["x"] . "," . $mostLikely["y"] . "\n";

    $startX = $mostLikely["x"] - $stepSize + 1; // - $stepSize was already explored
    $startY = $mostLikely["y"] - $stepSize + 1; // - $stepSize was already explored

    $endX = $mostLikely["x"] + $stepSize - 1;
    $endY = $mostLikely["y"] + $stepSize - 1;

    $refinedPositions = array();

    for($x = $startX; $x <= $endX; ++$x)
    {
        for($y = $startY; $y <= $endY; ++$y)
        {
            // Scan the whole picture
            $error = GetImageErrorAt($large, $small, $x, $y, 1); // now check every pixel!
            if($error["avg"] < $keepThreshold) // make the threshold smaller
            {
                array_push($refinedPositions, array("x" => $x, "y" => $y, "error" => $error));
            }
        }
    }

    echo "Found " . count($refinedPositions) . " refined positions\n";
    if(count($refinedPositions))
    {
        usort($refinedPositions, "SortOnAvgError");
        $mostLikely = $refinedPositions[0];
        echo "Most likely at " . $mostLikely["x"] . "," . $mostLikely["y"] . "\n";
    }
}

Found 8 potential positions
Most probably around 290,240
Checking between X 281 and 299
Checking between Y 231 and 249
Found 23 refined positions
Most likely at 288,235
in 13.960182189941 seconds

Found 123 potential positions
Most probably around 720,430
Found 17 refined positions
Most likely at 718,432
in 43.224536895752 seconds

$smallresizedwidth = $smallwidth / 2;
$smallresizedheight = $smallheight / 2;

$largeresizedwidth = $largewidth / 2;
$largeresizedheight = $largeheight / 2;

$smallresized = imagecreatetruecolor($smallresizedwidth, $smallresizedheight);
$largeresized = imagecreatetruecolor($largeresizedwidth, $largeresizedheight);

imagecopyresized($smallresized, $small, 0, 0, 0, 0, $smallresizedwidth, $smallresizedheight, $smallwidth, $smallheight);
imagecopyresized($largeresized, $large, 0, 0, 0, 0, $largeresizedwidth, $largeresizedheight, $largewidth, $largeheight);

array_push($potentialPositions, array("x" => $x * 2, "y" => $y * 2, "error" => $error));

imagedestroy($smallresized);
imagedestroy($largeresized);

Found 18 potential positions
Most around 720,440
Found 17 refined positions
Most likely at 718,432
in 11.499078989029 seconds

关于php - 使用PHP确定一个图像在另一个图像中的位置，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/14345256/