Using the two techniques, the image just takes 179 kB. The animation takes 270 steps and would take In this example a complete frame takes 5kB in the compressed GIF format. _Stepping_: use multiple frames for a single step of your animation, to minimize the area that needs to be redrawn. The library turns that clipping area into a frame. _Clipping_: mark the area that you want redrawn in the frame. The elaborate PONG example shows how you can keep the filesize small while creating a large number of frames, by the use of If the dog would be on a visible position at that time, it would disappear for an instance. But is also has an important drawback: in a looping, when all frames have drawn, a completely empty background image will be drawn.
This strategy helps keep the GIF image small, since the background does not need to be stored for every frame. This way, the background image remains and is ready to The strategy here is to start with a background image and use "restore to previous frame" to paint the pictures of the dog on top of it.įor each frame of the dogs animation, the GIF renderer draws the image (with transparent background), waits for the duration of the frame,Īnd then puts the image back into the state where it was before the image was drawn. These are transparent GIF images that are drawn and erased per frame. The following 46 frames show 10 different poses of Moki on different horizontal positions. In this example we find Moki running in the mountains.įrame 1 shows a background JPEG image. The horse image was taken from Wikipedia Moki The Horse example shows how to animate a series of same-sized images. Choose the strategy that best suits your needs.Ĭombinations of the strategies are also possible, since all settings are done on the frame level. The source code (directory "example") contains a few examples to help you on the way.Įach example shows a different animation strategy. Thanks a great deal to Matthew Flickinger for writing an awesome GIF format explanation Examples Use the global color table only when space requirements are much more important than GIF creation time requirements. The global color table is a color table that is shared by all frames that use it. To the pixels that show though from the page on which the image is located. While GIF allows you to _restore to background color_ at the end of a frame, browsers interpret this by "restoring" GIF (or rather Netscape's Application Block) does not allow you to start looping a subset of all frames. Impose a slowness fine for values of 0 and 1. However this frame takes up less space in the GIF.įrames are also much slower when StringCanvas is used.Ī duration of 2/100-ths of a second is the minimum, since browsers But in some cases it cannot be used, and compression is done in PHP, which is much slower.įrames are fast when GdCanvas or FileImageCanvas is used in combination with a local color table (the default).įrames are much slower when the global color table is used. The library uses GD's imagegif function to generate frames quickly. The duration of a frame in 1/100s of a secondĮxplicit use of global and local color tables (default = global)Įnd-of-frame actions: leave as is (= default), restore to previous frame, restore to backgroundĬreate a frame with GD lib functions (GdCanvas)Ĭreate frames based on a string of indexes and a color table array (StringCanvas) Specifying a color for transparent pixels Requires GD library (use `apt-get install php5-gd` or similar, to install) This library focuses on the use of GD in the creation of animated gif images. An Animated GIF creation library in pure PHP.
0 kommentar(er)
