PHP image processing (Part 2)

Picture background management

Before we learned how to create a canvas, we started from a blank, and then filled it with color, drawn points, text, etc. . Now we can load the background directly from an existing image. There are several commonly used functions:

imagecreatefrompng(), imagecreatefromjpeg(), imagecreatefromgif(). They indicate loading the corresponding image format.

In addition, we learn another function, getimagesize(), which returns an array with four cells. Index 0 contains the pixel value of the image width, and index 1 contains the pixel value of the image height. Index 2 is the mark of the image type: 1 = GIF, 2 = JPG, 3 = PNG,...

<?php
/**
 * 向不同的格式的图片中间画一个字符
 */
function image($imgfile, $string)
{
    list($width, $height, $type) = getimagesize($imgfile);
    $types = [&#39;1&#39; => &#39;git&#39;, &#39;2&#39; => &#39;jpeg&#39;, &#39;3&#39; => &#39;png&#39;];
    
    $createFunc = &#39;imagecreatefrom&#39; . $types[$type];
    $im = $createFunc($imgfile);
    
    $textColor = imagecolorallocate($im, 255, 0, 0);
    $x = ($width - imagefontwidth(5) * strlen($string)) / 2;
    $y = ($height - imagefontheight(5)) / 2;
   
    imagestring($im, 5, $x, $y, $string, $textColor);
    
    header("Content-type:image/".$types[$type]);
    $output = &#39;image&#39;.$types[$type];
    $output($im);
    imagedestroy($im);
}
//image(&#39;timg.jpg&#39;, &#39;jpg&#39;);
image(&#39;1.png&#39;, &#39;png&#39;);

Picture scaling and cropping

The following is a function that is very powerful and can Complete image scaling and cropping functions.

The function prototype is:

bool imagecopyresampled (
 resource $dst_image , 
 resource $src_image , 
 int $dst_x , 
 int $dst_y , 
 int $src_x , 
 int $src_y , 
 int $dst_w , 
 int $dst_h , 
 int $src_w , 
 int $src_h 
)

imagecopyresampled() Copies a square area in one image to another image, smoothly interpolating pixel values, so, in particular, reducing The size of the image is reduced while still maintaining great clarity.

Parameters

• dst_image Target image connection resource.

• src_image Source image connection resource.

• dst_x Target X coordinate point.

• dst_y Target Y coordinate point.

• src_x X coordinate point of the source.

• src_y Y coordinate point of the source.

• dst_w Target width.

• dst_h Target height.

• src_w The width of the source image.

• src_h The height of the source image.

Picture thumbnail

/**
 * 图片等比例缩放
 * @param string img 原图路径
 * @param int width 新图宽度
 * @param int height 新图高度
 */
function thumb($img, $width = 0, $height = 0)
{
    // 获取图片信息
    list($srcW, $srcH, $srcType) = getimagesize($img);
    $types = [1 => 'gif', 2 => 'jpeg', 3 => 'png'];
    $type  = $types[$srcType];
    
    // 原图资源句柄
    $create = 'imagecreatefrom' . $type;
    $srcIm  = $create($img);
    $ratioOrig = $srcW / $srcH;
    if ($width / $height > $ratioOrig) {
        $width = $height * $ratioOrig;
    } else {
        $height = $width / $ratioOrig;
    }
    
    // 新图资源
    $im = imagecreatetruecolor($width, $height);
    imagecopyresampled($im, $srcIm, 0, 0, 0, 0, 
        $width, $height, $srcW, $srcH);
    $output = 'image' . $type;
    header("content-type:image/$type");
    $output($im);
    imagedestroy($im);
    imagedestroy($srcIm);
}
//thumb('timg.jpg', 200, 150);
thumb('timg.jpg', 300, 10000);    
// 如想按某一边等比例缩放，只要把另一边值设为无限大即可

Picture cropping

/**
 * @param string $img 裁剪图路径
 * @param int $x 裁剪点x坐标
 * @param int $y 裁剪点y坐标
 * @param int $width 图片裁剪的宽度
 * @param int $height 图片裁剪的高度
 */
function crop ($img, $x, $y, $width, $height)
{
    // 获取图片信息
    $im = imagecreatetruecolor($width, $height);
    $srcType = getimagesize($img)[2];
    $types = [1 => 'gif', 2 => 'jpeg', 3=> 'png'];
    $type = $types[$srcType];
    // 原图资源句柄
    $create = 'imagecreatefrom' . $type;
    $srcIm = $create($img);
    // 裁剪图片
    imagecopyresampled($im, $srcIm, 0, 0,
         $x, $y, $width, $height, $width, $height);
    // 输出图片
    $output = 'image'.$type;
    header("content-type:image/$type");
    $output($im);
    imagedestroy($im);
    imagedestroy($srcIm);
}

Image watermark

Using imagecopyresampled can complete the function of image watermark, but here we learn another function imagecopy.

bool imagecopy(
 resource $dst_im,
    resource $src_im,
    int $dst_x, 
    int $dst_y, 
    int $src_x, 
    int $src_y, 
    int $src_w, 
    int $src_h
)

Copy the part of the src_im image whose coordinates start from src_x, src_y, have a width of src_w, and a height of src_h to the positions of the coordinates of dst_x and dst_y in the dst_im image.

<?php
// 图片水印
    
$dst = imagecreatefromjpeg(&#39;timg.jpg&#39;);
$src = imagecreatefromjpeg(&#39;php.jpg&#39;);

list($srcW, $srcH) = getimagesize(&#39;php.jpg&#39;);
imagecopy($dst, $src, 0, 0, 0, 0, $srcW, $srcH);

header("content-type:image/jpeg");
imagejpeg($dst);
imagedestroy($dst);
imagedestroy($src);

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