GD and Image 函数
PHP Manual

imagecopyresampled

(PHP 4 >= 4.0.6, PHP 5)

imagecopyresampled重采样拷贝部分图像并调整大小

说明

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() 将一幅图像中的一块正方形区域拷贝到另一个图像中,平滑地插入像素值,因此,尤其是,减小了图像的大小而仍然保持了极大的清晰度。成功时返回 TRUE, 或者在失败时返回 FALSE.

dst_imagesrc_image 分别是目标图像和源图像的标识符。如果源和目标的宽度和高度不同,则会进行相应的图像收缩和拉伸。坐标指的是左上角。本函数可用来在同一幅图内部拷贝(如果 dst_imagesrc_image 相同的话)区域,但如果区域交迭的话则结果不可预知。

Note:

因为调色板图像限制(255+1 种颜色)有个问题。重采样或过滤图像通常需要多于 255 种颜色,计算新的被重采样的像素及其颜色时采用了一种近似值。对调色板图像尝试分配一个新颜色时,如果失败我们选择了计算结果最接近(理论上)的颜色。这并不总是视觉上最接近的颜色。这可能会产生怪异的结果,例如空白(或者视觉上是空白)的图像。要跳过这个问题,请使用真彩色图像作为目标图像,例如用 imagecreatetruecolor() 创建的。

参数

dst_image

目标图象连接资源

src_image

源图象连接资源

dst_x

x-coordinate of destination point.

dst_y

y-coordinate of destination point.

src_x

x-coordinate of source point.

src_y

y-coordinate of source point.

dst_w

Destination width.

dst_h

Destination height.

src_w

源图象的宽度。

src_h

源图象的高度。

返回值

成功时返回 TRUE, 或者在失败时返回 FALSE.

范例

Example #1 Simple example

This example will resample an image to half its original size.

<?php
// The file
$filename 'test.jpg';
$percent 0.5;

// Content type
header('Content-Type: image/jpeg');

// Get new dimensions
list($width$height) = getimagesize($filename);
$new_width $width $percent;
$new_height $height $percent;

// Resample
$image_p imagecreatetruecolor($new_width$new_height);
$image imagecreatefromjpeg($filename);
imagecopyresampled($image_p$image0000$new_width$new_height$width$height);

// Output
imagejpeg($image_pnull100);
?>

以上例程的输出类似于:

Output of example : Simple example

Example #2 Resampling an image proportionally

This example will display an image with the maximum width, or height, of 200 pixels.

<?php
// The file
$filename 'test.jpg';

// Set a maximum height and width
$width 200;
$height 200;

// Content type
header('Content-Type: image/jpeg');

// Get new dimensions
list($width_orig$height_orig) = getimagesize($filename);

$ratio_orig $width_orig/$height_orig;

if (
$width/$height $ratio_orig) {
   
$width $height*$ratio_orig;
} else {
   
$height $width/$ratio_orig;
}

// Resample
$image_p imagecreatetruecolor($width$height);
$image imagecreatefromjpeg($filename);
imagecopyresampled($image_p$image0000$width$height$width_orig$height_orig);

// Output
imagejpeg($image_pnull100);
?>

以上例程的输出类似于:

Output of example : Resampling an image proportionally

注释

Note:

There is a problem due to palette image limitations (255+1 colors). Resampling or filtering an image commonly needs more colors than 255, a kind of approximation is used to calculate the new resampled pixel and its color. With a palette image we try to allocate a new color, if that failed, we choose the closest (in theory) computed color. This is not always the closest visual color. That may produce a weird result, like blank (or visually blank) images. To skip this problem, please use a truecolor image as a destination image, such as one created by imagecreatetruecolor().

参见

imagecopyresized() - 拷贝部分图像并调整大小


GD and Image 函数
PHP Manual