php can’t partially replace gd image

I’m trying to partially color an image based on my donation percentages, so the way i found was to copy a subbsection of a colored image, into the equivalent black and white image, so i could achieve a litle press meter with any image i want.

<?php
function createPartialGraycaleCopy($post_id, &$image_src_path,&$image_src_filename,&$bw_image_filename,$valor_currente,$objectivo)       {
    $post_thumbnail_id = get_post_thumbnail_id($post_id);
    // Find thumbnail locations
    $image_src = wp_get_attachment_image_src($post_thumbnail_id, 'thumbnail');
    $image_src_path = dirname($image_src[0]);
    $image_src_filename =substr(basename($image_src[0]), 0, strpos(basename($image_src[0]), "?")) ;

    // Create greyscale filename
    $image_src_extention_loc = (strripos($image_src_filename, '.') - strlen($image_src_filename));
    $bw_image_filename = substr($image_src_filename, 0, $image_src_extention_loc) . '_bw' . substr($image_src_filename, $image_src_extention_loc);

    // Get the local path of the image
    $wpcontent_image_path = dirname(get_attached_file($post_thumbnail_id));


    // Create greyscale image
    $bw_image = wp_load_image( $wpcontent_image_path . '/' . $image_src_filename);

    // Apply greyscale filter
    imagefilter($bw_image, IMG_FILTER_GRAYSCALE);

    header("Content-Type: image/jpeg"); 

    //Output the newly created image in jpeg format 
    ImageJpeg($image);                           // Save the image.
    imagejpeg($bw_image,$wpcontent_image_path . '/' . $bw_image_filename, 100);

    imagedestroy($bw_image);


   partialGrayscale($image_src_path,$image_src_filename,$bw_image_filename,$valor_currente,$objectivo)     ;
}         


function  partialGrayscale  ($image_src_path,$image_src_filename,$bw_image_filename,$valor_currente,$objectivo){
    // Create image instances
    $color = imagecreatefromjpeg($image_src_path . '/' . $image_src_filename);
    $saturated = imagecreatefromjpeg($image_src_path . '/' . $bw_image_filename);


    $percentagemCompleto=round((100*$valor_currente)/(100-$valor_currente));
    $comprimentoSaturado=imagesx($saturated)-(round(imagesx($saturated)*($percentagemCompleto/100)));
    $alturaSaturada=imagesy($saturated)-(round(imagesy($saturated)*($percentagemCompleto/100)));

    // Greyscale operation
   echo imagecopyresampled ($saturated, $color, 0, 0, 0, 0, $comprimentoSaturado, $alturaSaturada,$comprimentoSaturado, $alturaSaturada);   

    // Save the greyscale image file
    header("Content-Type: image/jpeg"); 

    //Output the newly created image in jpeg format 
                 // Save the image.
    imagejpeg($saturated,$wpcontent_image_path . '/' . $bw_image_filename, 100);
    // Remove original images from memory.
    imagedestroy($color);
    imagedestroy($saturated);
} 

?>

I can successfully create an black and white image but i can’t do the copy part.
What am i doing wrong?
Is there a better way to do this