如何调整图像保持约束php

Question

我已经制作了两个GIF来解释我想要做什么.灰色边框是我追求的尺寸(700*525).他们是这个问题的底部.

我希望所有大于给定宽度和高度的图像缩小到边界(从中心),然后裁剪边缘.以下是我将这些代码放在一起的一些代码:

if ($heightofimage => 700 && $widthofimage => 525){
    if ($heightofimage > $widthofimage){

        $widthofimage = 525;
        $heightofimage = //scaled height.

        //crop height to 700.

    }

    if ($heightofimage < $widthofimage){

        $widthofimage = //scaled width.
        $heightofimage = 700;

        //crop width to 525.

    }
}else{
    echo "image too small";
}

以下是一些可视化解释我想要实现的内容的GIF:

GIF 1:这里的图像比例是在太多了x方向

GIF 2:这里的图像比例是在太多了y方向

---

@timclutton的图像质量比较

所以我用你的方法用PHP(点击这里用php做你自己的测试),然后将它与原始照片进行比较,因为你可以看到有很大的不同!:

你的PHP方法:

http://tragicclothing.co.uk/video%20images/test/yo.jpg

实际文件:

---

Answer 1

下面的代码应该做你想要的.我没有对它进行过广泛的测试,但它似乎对我制作的几张测试图像起作用.在心灵的背后有一个令人尴尬的疑问,我的数学错误,但现在已经很晚了,我看不出任何明显的东西.

编辑:它已经足够琐碎我再次经历并发现了这个错误,即作物不在图像的中间.代码替换为工作版本.

简而言之:将此作为起点,而不是生产就绪代码!

<?php

// set image size constraints.
$target_w = 525;
$target_h = 700;

// get image.
$in = imagecreatefrompng('<path to your>.png');

// get image dimensions.
$w = imagesx($in);
$h = imagesy($in);

if ($w >= $target_w && $h >= $target_h) {
    // get scales.
    $x_scale = ($w / $target_w);
    $y_scale = ($h / $target_h);

    // create new image.
    $out = imagecreatetruecolor($target_w, $target_h);

    $new_w = $target_w;
    $new_h = $target_h;
    $src_x = 0;
    $src_y = 0;

    // compare scales to ensure we crop whichever is smaller: top/bottom or
    // left/right.
    if ($x_scale > $y_scale) {
        $new_w = $w / $y_scale;

        // see description of $src_y, below.
        $src_x = (($new_w - $target_w) / 2) * $y_scale;
    } else {
        $new_h = $h / $x_scale;

        // a bit tricky. crop is done by specifying coordinates to copy from in
        // source image. so calculate how much to remove from new image and
        // then scale that up to original. result is out by ~1px but good enough.
        $src_y = (($new_h - $target_h) / 2) * $x_scale;
    }

    // given the right inputs, this takes care of crop and resize and gives
    // back the new image. note that imagecopyresized() is possibly quicker, but
    // imagecopyresampled() gives better quality.
    imagecopyresampled($out, $in, 0, 0, $src_x, $src_y, $new_w, $new_h, $w, $h);

    // output to browser.
    header('Content-Type: image/png');
    imagepng($out);
    exit;

} else {
    echo 'image too small';
}

?>