如何计算裁剪图像的位置 - imagecopyresampled

Question

现在我的代码为我提供了一个具有正确按比例缩小的高度和宽度的图像，但使用了原始图像的顶部。我希望它使用图像的中心。但我不知道如何计算 imagecopyresampled 的 dst_y 值来执行此操作。谁能帮我解决:-)

<?php

function ReSize ($source,$destination,$dest_imagex,$dest_imagey,$quality) {

$source_image = imagecreatefromjpeg($source);
// Get dimensions of the original image
$source_imagex = imagesx($source_image);
$source_imagey = imagesy($source_image);

$after_width = $dest_imagex;

    //get the reduced width
    $reduced_width = ($source_imagex - $after_width);
    //now convert the reduced width to a percentage and round it to 2 decimal places
    $reduced_radio = round(($reduced_width / $source_imagex) * 100, 2);

    //ALL GOOD! let's reduce the same percentage from the height and round it to 2 decimal places.
    $reduced_height = round(($source_imagey / 100) * $reduced_radio, 2);
    //reduce the calculated height from the original height
    $after_height = $source_imagey - $reduced_height;

      $dst_y = 0; // The calculation I cannot figure out.....

$dest_image = imagecreatetruecolor($dest_imagex, $dest_imagey);
imagecopyresampled($dest_image, $source_image, 0, $dst_y, 0, 0, $after_width, $after_height, $source_imagex, $source_imagey);

$cache_folder = 'images/cache/';
$new_image = $cache_folder . rawurlencode($destination). '_' . $dest_imagex . 'x' . $dest_imagey . '.jpg';
imagejpeg($dest_image, $new_image,$quality);

echo $new_image;
}
?>

Answer 1

假设你想要一个 CSS “cover” 类型调整大小，你有两个选择：

• 垂直适合图像
• 水平适合的图片

先找到源和目标的比例：

$dest_ratio = $dest_imagex / $dest_imagey;
$source_ratio = $source_imagex / $source_imagey;

如果源比率大于目标比率，则意味着您需要水平拟合比例，否则需要垂直拟合比例。

---

水平拟合比例

imagecopyresampled(
    $dest_image,
    $source_image,
    0,
    0,
    0,
    ($source_imagey - ($source_imagex * $dest_ratio)) / 2,
    $dest_imagex,
    $dest_imagex * $source_ratio,
    $source_imagex,
    $source_imagey
);

---

垂直拟合比例

imagecopyresampled(
    $dest_image,
    $source_image,
    0,
    0,
    ($source_imagex - ($source_imagey / $dest_ratio)) / 2,
    0,
    $dest_imagey / $source_ratio,
    $dest_imagey,
    $source_imagex,
    $source_imagey
);

---

一起来：

function crop($source, $dest, $dest_imagex, $dest_imagey, $quality)
{
    $source_image = imagecreatefromjpeg($source);
    // Get dimensions of the original image
    $source_imagex = imagesx($source_image);
    $source_imagey = imagesy($source_image);
    $source_ratio = $source_imagey / $source_imagex;
    $dest_ratio = $dest_imagey / $dest_imagex;

    $dest_image = imagecreatetruecolor($dest_imagex, $dest_imagey);
    imagefill($dest_image, 0, 0, imagecolorallocate($dest_image, 255, 0, 0));

    if ($dest_ratio >= $source_ratio) {
        imagecopyresampled(
            $dest_image,
            $source_image,
            0,
            0,
            ($source_imagex - ($source_imagey / $dest_ratio)) / 2,
            0,
            $dest_imagey / $source_ratio,
            $dest_imagey,
            $source_imagex,
            $source_imagey
        );
    } else {
        imagecopyresampled(
            $dest_image,
            $source_image,
            0,
            0,
            0,
            ($source_imagey - ($source_imagex * $dest_ratio)) / 2,
            $dest_imagex,
            $dest_imagex * $source_ratio,
            $source_imagex,
            $source_imagey
        );
    }
    imagejpeg($dest_image, $dest, $quality);
}

用法

crop("image1.jpg", "image1_resized.jpg", 100, 100, 100);