$imagick = new Imagick($filePath);

$size = $imagick->getImageGeometry();
$width     = $size['width'];
$height    = $size['height'];
unset($size);

$textBottomPosition = $height-1;
$textRightPosition = $width;

$black = new ImagickPixel('#000000');
$gray  = new ImagickPixel('#C0C0C0');

$textRight  = 0;
$textLeft   = 0;
$textBottom = 0;
$textTop    = $height;

$foundGray = false;

for($x= 0; $x < $width; ++$x) {
    for($y = 0; $y < $height; ++$y) {
        $pixel = $imagick->getImagePixelColor($x,$y);
        $color = $pixel->getColor();
        // remove alpha component
        $pixel->setColor('rgb(' . $color['r'] . ','
                         . $color['g'] . ','
                         . $color['b'] . ')');

        // find the first gray pixel and ignore pixels below the gray
        if( $pixel->isSimilar($gray,.25) ) {
            $foundGray = true;
            break;
        }

        // find the text boundaries 
        if( $foundGray && $pixel->isSimilar($black,.25) ) {
            if( $textLeft === 0 ) {
                $textLeft = $x;
            } else {
                $textRight = $x;
            }

            if( $y < $textTop ) {
                $textTop = $y;
            }

            if( $y > $textBottom ) {
                $textBottom = $y;
            }
        }
    }
}

$textWidth = $textRight - $textLeft;
$textHeight = $textBottom - $textTop;
$imagick->cropImage($textWidth+10,$textHeight+10,$textLeft-5,$textTop-5);
$imagick->scaleImage($textWidth*10,$textHeight*10,true);

$textFilePath = tempnam('/temp','text-ocr-') . '.png';
$imagick->writeImage($textFilePath);

$text = str_replace(' ','',shell_exec('gocr ' . escapeshellarg($textFilePath)));
unlink($textFilePath);
var_dump($text);

您需要安装ImageMagick扩展和GOCR来运行它.
如果您不能或不想安装ImageMagick扩展名,我将向您发送一个具有函数来计算颜色距离的GD版本(它只是一个扩展的毕达哥拉斯定理).

不要忘记设置$filePath值.

该图像显示它查找一个灰色像素来更改$foundGray标志.之后,它会从左侧和从顶部查找第一个和最后一个像素.它用一些填充来裁剪图像,生成的图像被调整大小,并将其保存到临时文件中.之后,很容易使用gocr(或任何其他OCR命令或库).之后可以删除临时文件.