`CImage` is a PHP class which enables resizing of images through scaling and cropping together with filtering effects, all using PHP GD. The script `img.php` uses `CImage` to enable server-side image processing together with caching and optimization of the processed images.
Server-side image processing is a most useful tool for any web developer, `img.php` has an easy to use interface and its quite powerful when you integrate it with your website. Using it might decrease the time and effort put in managing images and improve your work flow when creating content for websites.
The `img.php` supports a lot of parameters. Combine the parameters to get the desired behavior and resulting image. For example, take the original image, resize it using width, aspect-ratio and crop-to-fit, apply a sharpen effect, save the image as JPEG using quality 30.
| `src` | Source image to use, mandatory. `src=img.png` or with subdirectory `src=dir/img.png`. |
| `nc, no-cache` | Do not use the cached version, do all image processing and save a new image to cache. |
| `so, skip-original`| Skip using the original image, always process image, create and use a cached version of the original image. |
| `v, verbose` | Do verbose output and print out a log what happens. Good for debugging, analyzing the process and inspecting how the image is being processed. |
####Options for resizing image
These options are all affecting the dimensions used when resizing the image. Its used to define the area to use in the source image and the resulting dimensions for the target image.
| `h, height` | `h=200` sets the width to be to max 200px. `h=25%` sets the height to max 25% of its original height. |
| `w, width` | `w=200` sets the height to be max 200px. `w=100%` sets the width to max 100% of its original width. |
| `ar, aspect-ratio` | Control target aspect ratio. Use together with either height or width or alone to base calculations on original image dimensions. This setting is used to calculate the resulting dimension for the image. `w=160&aspect-ratio=1.6` results in a height of 100px. Use ar=!1.6 to inverse the ratio, useful when using portrat instead of landscape images. |
| `nr, no-ratio, stretch` | Do *not* keep aspect ratio when resizing and using both width & height constraints. Results in stretching the image, if needed, to fit in the resulting box. |
| `a, area` | Define the area of the image to work with. Set `area=10,10,10,10` (top,right,bottom,left) to crop out the 10% of the outermost area. It works like an offset to define which part of the image you want to process. Its an alternative of using `crop`. |
| `c, crop` | Crops an area from the original image, set width, height, start_x and start_y to define the area to crop, for example `crop=100,100,10,10` (`crop=width,height,start_x,start_y`). Left top corner is 0, 0. You can use `left`, `right` or `center` when setting start_x. You may use `top`, `bottom` or `center` when setting start_y. |
####Processing of image before resizing
These options are executed *before* the image is resized.
| `s, scale` | Scale the image to a size proportional to a percentage of its original size, `scale=25` makes an image 25% of its original size and `size=200` doubles up the image size. Scale is applied before resizing and has no impact of the target width and height. |
####Processing of image after resizing
These options are executed *after* the image is resized.
| `sharpen` | Appy a filter that sharpens the image. |
| `emboss` | Appy a filter with an emboss effect. |
| `blur` | Appy a filter with a blur effect. |
| `f, filter` | Apply filter to image, `f=colorize,0,255,0,0` makes image more green. Supports all filters as defined in [PHP GD `imagefilter()`](http://php.net/manual/en/function.imagefilter.php). |
| `f0, f1-f9` | Same as `filter`, just add more filters. Applied in order `f`, `f0-f9`. |
| `q, quality` | Quality affects lossy compression and file size for JPEG images by setting the quality between 1-100, default is 60. Quality only affects JPEG. |
| `co, compress` | For PNG images it defines the compression algorithm, values can be 0-9, default is defined by PHP GD. Compress only affects PNG. |
| `p, palette` | Create a palette version of the image with up to 256 colors. |
| `sa, save-as` | Save resulting image as JPEG, PNG or GIF, for example `?src=river.png&save-as=gif`. |
* Adding option `dpr, device-pixel-ratio` which defaults to 1. Set to 2 to get a twice as large image. Useful for Retina displays. Basically a shortcut to enlarge the image.
