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
$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_image
和 src_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_image 和 src_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, $image, 0, 0, 0, 0, $new_width, $new_height, $width, $height);
// Output
imagejpeg($image_p, null, 100);
?>
以上例程的输出类似于：
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, $image, 0, 0, 0, 0, $width, $height, $width_orig, $height_orig);
// Output
imagejpeg($image_p, null, 100);
?>
以上例程的输出类似于：
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