How header() outputs image cache usage example
When we generate the verification code, we need to directly input the image, usually using header("Content-type: image/jpeg"); to achieve this. Here is a brief introduction.
In many developments, we try to use header("Content-type: image/jpeg"); to output pictures, and try to use some php image processing technology to allow the output Pictures are more intelligent and dynamic. But we often encounter new problems. Unless you specify different URL structures and use server technology to cache images, it is very likely that these output images will consume a lot of traffic. How to cache them and call the cache the next time the user visits? (The premise is that you want this image to remain unchanged)
// put this above any php image generation code:
session_start();
header("Cache-Control: private, max-age=10800, pre-check=10800");
header("Pragma: private");
header("Expires: " . date(DATE_RFC822,strtotime(" 2 day")));Add the above code above header("Content-type: image/jpeg");, which will specify the cache time of the current page (two days) and use this cache time node on the next visit.
Next, determine whether there is already a cache. If so, use the cache.
Situation 1: If the browser already caches the current page, then use it directly.
// the browser will send a $_SERVER['HTTP_IF_MODIFIED_SINCE'] if it has a cached copy
if(isset($_SERVER['HTTP_IF_MODIFIED_SINCE'])){
// if the browser has a cached version of this image, send 304
header('Last-Modified: '.$_SERVER['HTTP_IF_MODIFIED_SINCE'],true,304);
exit;
}Scenario 2: The browser caches the current page. Although we have updated some image information, the source image itself has not changed, and we want to use the previous cache, so we also use the cache.
$img = "some_image.png";
if (isset($_SERVER['HTTP_IF_MODIFIED_SINCE']) && (strtotime($_SERVER['HTTP_IF_MODIFIED_SINCE']) ==
filemtime($img))) {
// send the last mod time of the file back
header('Last-Modified: '.gmdate('D, d M Y H:i:s', filemtime($img)).' GMT',true, 304);
exit;
} Of course, there are some special situations that we must consider, but the above code can basically lead our thinking. By the way, remember to put them all above header("Content-type: image/jpeg").
Let’s take a look at an example
<?php
//调整图片大小
/**
*图片按比例调整大小的原理：
*1、比较原图大小是否小于等于目标大小，如果是则直接采用原图宽高
*2、如果原图大小超过目标大小，则对比原图宽高大小
*3、如：宽>高，则宽=目标宽, 高=目标宽的比例 * 原高
*4、如：高>宽，则高=目标高，宽=目标高的比例 * 原宽
**/
$image = "test.jpg";
$max_width = 200;
$max_height = 200;
$size = getimagesize($image); //得到图像的大小
$width = $size[0];
$height = $size[1];
$x_ratio = $max_width / $width;
$y_ratio = $max_height / $height;
if (($width <= $max_width) && ($height <= $max_height))
{
$tn_width = $width;
$tn_height = $height;
}
elseif (($x_ratio * $height) < $max_height)
{
$tn_height = ceil($x_ratio * $height);
$tn_width = $max_width;
}
else
{
$tn_width = ceil($y_ratio * $width);
$tn_height = $max_height;
}
$src = imagecreatefromjpeg($image);
$dst = imagecreatetruecolor($tn_width, $tn_height); //新建一个真彩色图像
imagecopyresampled($dst, $src, 0, 0, 0, 0,$tn_width, $tn_height, $width, $height); //重采样拷贝部分图像并调整大小
header('Content-Type: image/jpeg');
imagejpeg($dst,null,100);
imagedestroy($src);
imagedestroy($dst);
?>The above is the detailed content of How header() outputs image cache usage example. For more information, please follow other related articles on the PHP Chinese website!
Hot AI Tools
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Undress AI Tool
Undress images for free
Clothoff.io
AI clothes remover
Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!
Hot Article
Hot Tools
Notepad++7.3.1
Easy-to-use and free code editor
SublimeText3 Chinese version
Chinese version, very easy to use
Zend Studio 13.0.1
Powerful PHP integrated development environment
Dreamweaver CS6
Visual web development tools
SublimeText3 Mac version
God-level code editing software (SublimeText3)
Hot Topics
How to solve the problem of automatically saving pictures when publishing on Xiaohongshu? Where is the automatically saved image when posting?
Mar 22, 2024 am 08:06 AM
With the continuous development of social media, Xiaohongshu has become a platform for more and more young people to share their lives and discover beautiful things. Many users are troubled by auto-save issues when posting images. So, how to solve this problem? 1. How to solve the problem of automatically saving pictures when publishing on Xiaohongshu? 1. Clear the cache First, we can try to clear the cache data of Xiaohongshu. The steps are as follows: (1) Open Xiaohongshu and click the "My" button in the lower right corner; (2) On the personal center page, find "Settings" and click it; (3) Scroll down and find the "Clear Cache" option. Click OK. After clearing the cache, re-enter Xiaohongshu and try to post pictures to see if the automatic saving problem is solved. 2. Update the Xiaohongshu version to ensure that your Xiaohongshu
How to post pictures in TikTok comments? Where is the entrance to the pictures in the comment area?
Mar 21, 2024 pm 09:12 PM
With the popularity of Douyin short videos, user interactions in the comment area have become more colorful. Some users wish to share images in comments to better express their opinions or emotions. So, how to post pictures in TikTok comments? This article will answer this question in detail and provide you with some related tips and precautions. 1. How to post pictures in Douyin comments? 1. Open Douyin: First, you need to open Douyin APP and log in to your account. 2. Find the comment area: When browsing or posting a short video, find the place where you want to comment and click the "Comment" button. 3. Enter your comment content: Enter your comment content in the comment area. 4. Choose to send a picture: In the interface for entering comment content, you will see a "picture" button or a "+" button, click
6 Ways to Make Pictures Sharper on iPhone
Mar 04, 2024 pm 06:25 PM
Apple's recent iPhones capture memories with crisp detail, saturation and brightness. But sometimes, you may encounter some issues that may cause the image to look less clear. While autofocus on iPhone cameras has come a long way, allowing you to take photos quickly, the camera can mistakenly focus on the wrong subject in certain situations, making the photo blurry in unwanted areas. If your photos on your iPhone look out of focus or lack sharpness overall, the following post should help you make them sharper. How to Make Pictures Clearer on iPhone [6 Methods] You can try using the native Photos app to clean up your photos. If you want more features and options
How to make ppt pictures appear one by one
Mar 25, 2024 pm 04:00 PM
In PowerPoint, it is a common technique to display pictures one by one, which can be achieved by setting animation effects. This guide details the steps to implement this technique, including basic setup, image insertion, adding animation, and adjusting animation order and timing. Additionally, advanced settings and adjustments are provided, such as using triggers, adjusting animation speed and order, and previewing animation effects. By following these steps and tips, users can easily set up pictures to appear one after another in PowerPoint, thereby enhancing the visual impact of the presentation and grabbing the attention of the audience.
What should I do if the images on the webpage cannot be loaded? 6 solutions
Mar 15, 2024 am 10:30 AM
Some netizens found that when they opened the browser web page, the pictures on the web page could not be loaded for a long time. What happened? I checked that the network is normal, so where is the problem? The editor below will introduce to you six solutions to the problem that web page images cannot be loaded. Web page images cannot be loaded: 1. Internet speed problem The web page cannot display images. It may be because the computer's Internet speed is relatively slow and there are more softwares opened on the computer. And the images we access are relatively large, which may be due to loading timeout. As a result, the picture cannot be displayed. You can turn off the software that consumes more network speed. You can go to the task manager to check. 2. Too many visitors. If the webpage cannot display pictures, it may be because the webpages we visited were visited at the same time.
How to convert pdf documents into jpg images with Foxit PDF Reader - How to convert pdf documents into jpg images with Foxit PDF Reader
Mar 04, 2024 pm 05:49 PM
Are you also using Foxit PDF Reader software? So do you know how Foxit PDF Reader converts pdf documents into jpg images? The following article brings you how Foxit PDF Reader converts pdf documents into jpg images. For those who are interested in the method of converting jpg images, please come and take a look below. First start Foxit PDF Reader, then find "Features" on the top toolbar, and then select the "PDF to Others" function. Next, open a web page called "Foxit PDF Online Conversion". Click the "Login" button on the upper right side of the page to log in, and then turn on the "PDF to Image" function. Then click the upload button and add the pdf file you want to convert into an image. After adding it, click "Start Conversion"
How to arrange two pictures side by side in wps document
Mar 20, 2024 pm 04:00 PM
When using WPS office software, we found that not only one form is used, tables and pictures can be added to the text, pictures can also be added to the table, etc. These are all used together to make the content of the entire document look richer. , if you need to insert two pictures into the document and they need to be arranged side by side. Our next course can solve this problem: how to place two pictures side by side in a wps document. 1. First, you need to open the WPS software and find the picture you want to adjust. Left-click the picture and a menu bar will pop up, select "Page Layout". 2. Select "Tight wrapping" in text wrapping. 3. After all the pictures you need are confirmed to be set to "Tight text wrapping", you can drag the pictures to the appropriate position and click on the first picture.
How to view and refresh dns cache in Linux
Mar 07, 2024 am 08:43 AM
DNS (DomainNameSystem) is a system used on the Internet to convert domain names into corresponding IP addresses. In Linux systems, DNS caching is a mechanism that stores the mapping relationship between domain names and IP addresses locally, which can increase the speed of domain name resolution and reduce the burden on the DNS server. DNS caching allows the system to quickly retrieve the IP address when subsequently accessing the same domain name without having to issue a query request to the DNS server each time, thereby improving network performance and efficiency. This article will discuss with you how to view and refresh the DNS cache on Linux, as well as related details and sample code. Importance of DNS Caching In Linux systems, DNS caching plays a key role. its existence
