Webdesign:PHP:How to Resize Image Dynamically in PHP
Mthumb is a PHP tool for resizing images on the fly. It is a better and securer version of TimThumb.
Here are the major changes:
- Removed the WebShots features entirely
- Removed the PHP Memory settings entirely
- Disabled all remote/external sites by default
- Removed option to allow all remote sites
- Changed cache folder to use system cache by default
- Increased default caching time and time between cleans
- Increased default allowed file size and dimensions
- Enabled PNG compression by default
- Enabled PNG transparency by default
- Removed error output that revealed script versions and error images
- Tilde support in URLs (for user home directories was added)
- Code cleanup and PHP docblock comments
- Added check to ensure class was defined before calling start method
Download from Github
| stands for | values | What it does | |
|---|---|---|---|
| src | source | url to image | Tells mThumb which image to resize › mThumb basic properties tutorial |
| w | width | the width to resize to | Remove the width to scale proportionally (will then need the height) › mThumb width tutorial |
| h | height | the height to resize to | Remove the height to scale proportionally (will then need the width) › mThumb height tutorial |
| q | quality | 0 – 100 | Compression quality. The higher the number the nicer the image will look. I wouldn’t recommend going any higher than about 95 else the image will get too large › mThumb image quality tutorial |
| a | alignment | c, t, l, r, b, tl, tr, bl, br | Crop alignment. c = center, t = top, b = bottom, r = right, l = left. The positions can be joined to create diagonal positions › mThumb crop position tutorial |
| zc | zoom / crop | 0, 1, 2, 3 | Change the cropping and scaling settings › mThumb crop scaling tutorial |
| f | filters | too many to mention | Let’s you apply image filters to change the resized picture. For instance you can change brightness/ contrast or even blur the image › mThumb image filter tutorial |
| s | sharpen | Apply a sharpen filter to the image, makes scaled down images look a little crisper › tutorial | |
| cc | canvas colour | hexadecimal colour value (#ffffff) | Change background colour. Most used when changing the zoom and crop settings, which in turn can add borders to the image. |
| ct | canvas transparency | true (1) | Use transparency and ignore background colour |
There are a whole bunch of settings that are not controlled by the normal query string parameters.
| constant | values | What it does |
|---|---|---|
| DEBUG_ON | true/ false | Turn on debug logging to the standard PHP error log |
| DEBUG_LEVEL | 1, 2, 3 | Debug level 1 is less noisy and level 3 is the most noisy |
| ALLOW_EXTERNAL | true/ false | Allow images from external sites to be resized. Restricted to the images defined in the $allowed_sites array. |
| FILE_CACHE_ENABLED | true/ false | Should we cache the files on disk to speed up your website? (hint: the answer is yes, unless you’re testing/ developing things! :)) |
| FILE_CACHE_TIME_BETWEEN_CLEANS | 86400 (milliseconds) | mThumb automatically cleans up the cached files. This defines the amount of time between the different the cache cleaning. |
| FILE_CACHE_MAX_FILE_AGE | 86400 (milliseconds) | How old should a file be before it’s cleaned? |
| FILE_CACHE_SUFFIX | .txt | What to put at the end of all files in the cache directory so we can identify them easily |
| FILE_CACHE_PREFIX | mthumb | What to put at the start of the cache files so we can identify them easily |
| FILE_CACHE_DIRECTORY | .system temporary directory |
the name of the image cache directory. Left blank it will use the system temporary directory (which is better for security, but is not supported by all web hosts) |
| MAX_FILE_SIZE | 10485760 | 10 Megs is 10485760. This is the max internal or external file size that we’ll process |
| CURL_TIMEOUT | 20 | Timeout duration for Curl. This only applies if you have Curl installed and aren’t using PHP’s default URL fetching mechanism. |
| WAIT_BETWEEN_FETCH_ERRORS | 20 | Time to wait between errors fetching remote file. |
| BROWSER_CACHE_MAX_AGE | 864000 | Browser cache duration (to prevent images from being reloaded more than once – the higher the number the better). |
| BROWSER_CACHE_DISABLE | true/ false | Use for testing if you want to disable browser caching. |
| MAX_WIDTH | 3600 | Put a sensible limit of the width of the resized image (so that crazy large images can’t be created) |
| MAX_HEIGHT | 3600 | Put a sensible limit of the height of the resized image (so that crazy large images can’t be created) |
| PNG_IS_TRANSPARENT | TRUE | Define if a png image should have a transparent background color. Use False value if you want to display a custom coloured canvas_colour |