Question

我正在尝试使用图像的某些部分来裁剪图像，但还希望在图像周围添加“额外”空间。但是，当裁剪后的图像在“多余”空间中产生黑色空间时，我希望它是透明的。

使用裁剪器JavaScript获取裁剪坐标：https://fengyuanchen.github.io/cropperjs/

然后使用PHP imagecopyresample d裁剪图像到所需大小。

图像的裁剪很好，但是，如果我将图像裁剪为大于原始尺寸，则会在图像周围增加黑色空间，我想将其更改为透明。

本来可以在裁剪后的图像中搜索黑色像素并将其转换为透明像素，但是当图像中有黑色像素时，这种想法就会失效

 Current php code: (asuming file type is PNG)

 //$cropData 
 //is an array of data passed through from the cropper containing the original width and height, new width and height and the cropping x and y coordinates.

 //passed in image to be cropped
 $current_image = "/folder/example.jpg";

 //image file location of cropped image
 $image_name = "/folder/cropped_example.jpg";


 //create blank image of desired crop size
 $width = $cropData["width"];
 $height = $cropData["height"];
 $background = imagecreatetruecolor($width, $height);

 //crop coordinates
 $crop_x = $cropData["x"];
 $crop_y = $cropData["y"];

 //create resouce image of current image to be cropped
 $image = imagecreatefrompng($current_image);

 //crop image
 imagecopyresampled($background, $image, 0, 0, $crop_x, $crop_y, $width, $height, $width, $height)){


 imagepng($background, $image_name);


 //File Uploaded... return to page

Answer 1

首先，您需要通过将true传递到imagesavealpha来启用Alpha通道
下一步是通过将false传递到imagealphablending来禁用alphablending，否则alpha通道将用于重新计算颜色，并且其值将丢失。
为imagecolorallocatealpha分配将127作为alpha值传递的透明颜色
以此颜色填充源图像的背景（例如调用imagefilledrectangle）
将源宽度和高度参数传递到imagecopyresampled时不要超出图像的实际尺寸，否则，越界区域将被视为不透明的黑色。

示例：

 $background = imagecreatetruecolor($width, $height);

 //crop coordinates
 $crop_x = 10;
 $crop_y = 10;

 imagesavealpha($background, true); // alpha chanel will be preserved
 imagealphablending($background, false); // disable blending operations
 $transparent_color = imagecolorallocatealpha($background, 0, 0, 0, 127); // allocate transparent
 imagefilledrectangle($background, 0, 0, $width, $height, $transparent_color); // fill background

 //create resouce image of current image to be cropped
 $image = imagecreatefrompng($current_image);

 // Limit source sizes;
 $minw = min($width, imagesx($image));
 $minh = min($height, imagesy($image));

 //crop image
 imagecopyresampled($background, $image, 0, 0, $crop_x, $crop_y, $minw, $minh, $minw, $minh);

 imagepng($background, $image_name);
 // done!

将图像裁切成大于原始尺寸

1 个答案: