272 lines
7.4 KiB
JavaScript
272 lines
7.4 KiB
JavaScript
/*
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TODOs:
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Fo sho:
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- Show a progress bar when buffering
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- use document.body.offsetWidth where present? (instead of window.innerWidth, the former excludes the width of scrollbars)
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- scroll two pages at a time in double page mode
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- manga mode
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- page controls
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- thumbnail browser
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- chrome frame
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Nice 2 have:
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- remember position (use localStorage)
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- maybe use local storage for the pages array too? might be easier to implement manga mode with that
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- offline mode
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- page turn animation
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*/
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var book
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window.onload = function() {
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var pages = [
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"http://dev.justforcomics.com/get/image/?f=comics/extracted/oni_whiteout_melt_1/00.jpg",
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"http://dev.justforcomics.com/get/image/?f=comics/extracted/oni_whiteout_melt_1/01.jpg",
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"http://dev.justforcomics.com/get/image/?f=comics/extracted/oni_whiteout_melt_1/02.jpg",
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"http://dev.justforcomics.com/get/image/?f=comics/extracted/oni_whiteout_melt_1/03.jpg",
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"http://dev.justforcomics.com/get/image/?f=comics/extracted/oni_whiteout_melt_1/04.jpg",
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"http://dev.justforcomics.com/get/image/?f=comics/extracted/oni_whiteout_melt_1/05.jpg",
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"http://dev.justforcomics.com/get/image/?f=comics/extracted/oni_whiteout_melt_1/06.jpg"
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];
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var options = {
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displayMode: "double",
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zoomMode: "fitWidth"
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}
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book = new ComicBook("comic", pages, options);
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book.draw();
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}
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window.onresize = function() {
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book.draw();
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}
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function ComicBook(id, srcs, opts) {
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this.id = id;
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this.srcs = srcs;
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var defaults = {
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displayMode: "double", // single / double
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zoomMode: "fitWidth" // manual / fitWidth
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}
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var options = merge(defaults, opts);
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var pages = [];
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var canvas;
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var context;
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var buffer = 4;
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var pointer = 0;
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var loaded = 0;
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var scale = 1;
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/*
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* @param {String} id The canvas ID to draw the comic on.
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* @param {Object} srcs An array of all the comic page srcs, in order
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* @see #preload
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*/
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ComicBook.prototype.draw = function() {
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// setup canvas
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canvas = document.getElementById(this.id);
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context = canvas.getContext("2d");
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// preload images if needed
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if (pages.length != this.srcs.length) this.preload(this.srcs);
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else this.drawPage();
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// add page controls
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canvas.addEventListener("click", ComicBook.prototype.navigation, false);
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}
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/*
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* Zoom the canvas
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*
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* @param new_scale {Number} Scale the canvas to this ratio
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*/
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ComicBook.prototype.zoom = function(new_scale) {
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options.zoomMode = "manual";
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scale = new_scale;
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if (typeof pages[pointer] == "object") this.drawPage();
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}
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/**
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* Preload all images, draw the page only after a given number have been loaded.
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*
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* @param srcs {Object} srcs
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* @see #drawPage
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*/
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ComicBook.prototype.preload = function(srcs) {
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if (srcs.length < buffer) buffer = srcs.length; // don't get stuck if the buffer level is higher than the number of pages
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srcs.forEach(function(src, i) {
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var page = new Image();
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page.src = src;
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page.onload = function() {
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pages[i] = this;loaded++;
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if (loaded == buffer) ComicBook.prototype.drawPage();
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}
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});
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}
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/**
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* Draw the current page in the canvas
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*
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* TODO: break this down into drawSinglePage() & drawDoublePage()
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* TODO: if the current browser doesn't have canvas support, use img tags
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*/
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ComicBook.prototype.drawPage = function() {
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var zoom_scale;
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var offsetW = 0, offsetH = 0;
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var page = pages[pointer];
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var page2 = pages[pointer + 1];
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if (typeof page != "object") throw "invalid page type '"+ typeof page +"'";
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var width = page.width;
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if (options.displayMode == "double") {
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// for double page spreads, factor in the width of both pages
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if (typeof page2 == "object") width += page2.width;
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// if this is the last page and there is no page2, still keep the canvas wide
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else width += width;
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}
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// update the page scale if a non manual mode has been chosen
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switch(options.zoomMode) {
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case "manual":
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zoom_scale = (options.displayMode == "double") ? scale * 2 : scale;
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break;
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case "fitWidth":
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zoom_scale = (window.innerWidth > width)
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? ((window.innerWidth - width) / window.innerWidth) + 1 // scale up if the window is wider than the page
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: window.innerWidth / width; // scale down if the window is narrower than the page
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break;
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default:throw "invalid zoomMode";
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}
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var canvas_width = page.width * zoom_scale;
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var canvas_height = page.height * zoom_scale;
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var page_width = (options.zoomMode == "manual") ? page.width * scale : canvas_width;
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var page_height = (options.zoomMode == "manual") ? page.height * scale : canvas_height;
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canvas_height = page_height;
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// make sure the canvas is always at least full screen, even if the page is more narrow than the screen
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canvas.width = (canvas_width < window.innerWidth) ? window.innerWidth : canvas_width;
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canvas.height = (canvas_height < window.innerHeight) ? window.innerHeight : canvas_height;
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// work out a horizonal position that will keep the pages always centred
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if (canvas_width < window.innerWidth && options.zoomMode == "manual") {
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offsetW = (window.innerWidth - page_width) / 2;
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if (options.displayMode == "double") offsetW = offsetW - page_width / 2;
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}
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// work out a vertical position that will keep the pages always centred
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if (canvas_height < window.innerHeight && options.zoomMode == "manual") {
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offsetH = (window.innerHeight - page_height) / 2;
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}
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// draw the page(s)
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context.drawImage(page, offsetW, offsetH, page_width, page_height);
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if (options.displayMode == "double" && typeof page2 == "object") context.drawImage(page2, page_width + offsetW, offsetH, page_width, page_height);
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}
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/**
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* Increment the counter and draw the page in the canvas
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*
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* @see #drawPage
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*/
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ComicBook.prototype.drawNextPage = function() {
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if (pointer + 1 < pages.length) {
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pointer++;
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this.drawPage();
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}
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}
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/**
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* Decrement the counter and draw the page in the canvas
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*
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* @see #drawPage
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*/
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ComicBook.prototype.drawPrevPage = function() {
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if (pointer > 0) {
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pointer--;
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this.drawPage();
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}
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}
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ComicBook.prototype.navigation = function(e) {
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switch (e.type) {
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case "click":
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switch (getCursorPosition(e)) {
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case "left": ComicBook.prototype.drawPrevPage(); break;
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case "right": ComicBook.prototype.drawNextPage(); break;
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}
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break;
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}
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}
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/**
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* Figure out the cursor position relative to the canvas.
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*
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* Thanks to: Mark Pilgrim & http://diveintohtml5.org/canvas.html
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*/
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function getCursorPosition(e) {
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var x;
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// check if page relative positions exist
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if (e.pageX) x = e.pageX;
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// if not figure them out
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else x = e.clientX + document.body.scrollLeft + document.documentElement.scrollLeft;
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// make the position relative to the canvas
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x -= canvas.offsetLeft;
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// check if the user clicked on the left or right side
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return (x <= canvas.width / 2) ? 'left' : 'right';
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}
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/**
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* Merge two arrays. Any properties in b will replace the same properties in
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* a. New properties from b will be added to a.
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*
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* @param a {Object}
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* @param b {Object}
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*/
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function merge(a, b) {
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if (typeof b == "undefined") b = {};
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for (prop in a) {
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if (prop in b) continue;
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b[prop] = a[prop];
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}
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return b;
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}
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}
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