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HiddenCanvas.dart
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HiddenCanvas.dart
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part of BigIsland;
// Big Island video game source code file
// Copyright (C) 2012 Severin Ibarluzea
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
class HiddenCanvas {
html.CanvasElement canvas;
html.CanvasRenderingContext2D context;
HiddenCanvas(int width,int height){
canvas = new html.Element.tag("canvas");
canvas.width = width;
canvas.height = height;
context = canvas.getContext("2d");
}
//Get image from canvas
html.ImageElement getImage(callback){
html.ImageElement img = new html.Element.tag("img");
String dataURL = canvas.toDataUrl("image/png");
img.onLoad.listen((e){
callback(img);
});
img.src = dataURL;
return img;
}
//Split provided image into many images
static List<html.ImageElement> split(html.ImageElement img,int px,int py,Function callback){
//TODO we shouldn't be drawing the entire image for every image split
HiddenCanvas hc = new HiddenCanvas(px,py);
html.CanvasRenderingContext2D c = hc.context;
int n = 0;
int amt = 0;
List<html.ImageElement> list = new List<html.ImageElement>();
//TODO better way to fill list with null?
while(list.length<(img.width/px) * (img.height/py)){list.add(null);}
void addToList(int n){
hc.getImage((img){
list[n] = img;
amt ++;
if (amt >= list.length){
callback(list);
}
});
}
for(int y = 0;y>-img.height;y-=py){
for (int x = 0;x>-img.width;x-=px){
c.clearRect(0, 0, px, py);
c.drawImage(img, x, y);
addToList(n++);
}
}
}
}