JavaScript picture pre-loaded to make picture pixels clearer

3. When the client requests the map, 4M of the original image will not immediately under the good, especially the remote network, then first put the small map down, and pulled up to the original size (this operation should be the use of no interpolation algorithm direct amplification, speed is very fast.) ）

Should be stored in a number of different sizes and different resolution of many pictures, when the big picture did not load the first successive display of small pictures, and finally show the big picture

The code is as follows	Copy Code
var img = new Image (); IMG.SRC = "Yun_qi_img/big_800_600.jpg"; Img.onload = function () { document.getElementById (' myimage '). src = this.src; }

JavaScript image Pre-loading technology

Lightbox class effects use preload to center the picture and need to wait for the full load to be displayed and experience poorly (such as the full screen effect of the Filick album). JavaScript cannot get IMG header data, is that really the case? This article is an ingenious way to get JavaScript to get it.

This is an example of how most people use preload to get the size of a picture:

Of course there will be some compatible traps, such as width and height to detect the inconsistencies of each browser, as well as WebKit new image () created by the image in the loading process with the URL image, after repeated testing the best way to deal with:

The code is as follows

Copy Code

Update: 05.27:1. Ensure callback execution order: error > Ready > Load;2, callback function This points to the IMG itself 04-02:1, increase the picture after full load callback 2, improve performance /** * Picture header Data Load Ready event-get picture size faster * @version 2011.05.27 * @author Tangbin * @param {String} picture path * @param {Function} dimensions ready * @param {Function} loaded complete (optional) * @param {Function} load error (optional) * @example imgready (' Yun_qi_img/logo_cn.png ', function () { Alert (' Size ready:width= ' + this.width + '; height= ' + this.height); }); */ var Imgready = (function () { var list = [], intervalid = null, Used to execute queues tick = function () { var i = 0; for (; i < list.length; i++) { List[i].end? List.splice (i--, 1): List[i] (); }; !list.length && Stop (); }, Stop all timer queues stop = function () { Clearinterval (Intervalid); Intervalid = null; }; return function (URL, ready, load, error) { var onready, width, height, newwidth, Newheight, img = new Image (); img.src = URL; If the picture is cached, the cached data is returned directly if (img.complete) { Ready.call (IMG); Load && load.call (IMG); Return }; width = img.width; Height = img.height; Events after loading errors Img.onerror = function () { Error && Error.call (IMG); Onready.end = true; img = img.onload = Img.onerror = null; }; Picture size Ready Onready = function () { Newwidth = Img.width; Newheight = Img.height; if (newwidth!== width | | | newheight!== Height | | If the picture has been loaded elsewhere, the usable area can be detected Newwidth * newheight > 1024 ) { Ready.call (IMG); Onready.end = true; }; }; Onready (); Fully Loaded Events Img.onload = function () { OnLoad may be faster than Onready in the timer time difference range Check here and ensure Onready priority !onready.end && Onready (); Load && load.call (IMG); IE gif animation will loop to execute onload, empty onload can be img = img.onload = Img.onerror = null; }; To join a queue for periodic execution if (!onready.end) { List.push (Onready); Reduces browser performance loss whenever only one timer is allowed if (intervalid = = null) Intervalid = SetInterval (tick, 40); }; }; })();

Call Example:

The code is as follows	Copy Code
Imgready (' Yun_qi_img/logo_cn.png ', function () { Alert (' Size ready:width= ' + this.width + '; height= ' + this.height); });