Keyboard Controlled Pixel Drawing

anilashanbhag

The script is used in my newest chrome app
https://chrome.google.com/webstore/developer/detail/bomkcodcgmbjjhogdjophonfhgpegoni/

Site:
http://codestrix.co.cc/pixels/

The above script is a good to get stated with HTML5 canvas.
Much of it is named so as to be self explanatory but any doubts you are more than welcome to post it here.

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About the Author
var currentx = 350;
	var currenty = 350;
	var ltArrow = 37;
	var upArrow = 38;
	var rtArrow = 39;
	var dwArrow = 40;
	var size = 50;

	
function keyHit(evt) {
	var oCanvas = document.getElementById('oCanvas');
	var oCtx = oCanvas.getContext('2d');
	var thisKey;
	if (evt) {
		thisKey = evt.which;
	}
	else {
		thisKey = window.event.keyCode;
	}
	switch(thisKey){
		case ltArrow:
			currentx -= size;
			if(currentx<0){currentx = 0;}
			oCtx.fillRect(currentx, currenty, size, size);
			break;
		case rtArrow:
			currentx += size;
			if(currentx>800-size){currentx = 800-size;}
			oCtx.fillRect(currentx, currenty, size, size);
			break;
		case upArrow:
			currenty -= size;
			if(currenty<0){currenty = 0;}
			oCtx.fillRect(currentx, currenty, size, size);
			break;
		case dwArrow:
			currenty += size;
			if(currenty>800-size){currenty=800-size;}
			oCtx.fillRect(currentx, currenty, size, size);
			break;
		default:
			break;
	}
return False;
}

function resetSize(){
	var newLoc = document.getElementById("size");
	newLoc.blur();
	var newSize = newLoc.options[newLoc.selectedIndex].value;
	size = parseInt(newSize);
}

function resetColor(){
	var newLoca = document.getElementById("color");
	newLoca.blur();
	var newColor = newLoca.options[newLoca.selectedIndex].value;
	var oCanvas = document.getElementById('oCanvas');
	var oCtx = oCanvas.getContext('2d');
	oCtx.fillStyle = newColor;
}
	
window.onload = init;

function init(){
	var oCanvas = document.getElementById('oCanvas');
	var iWidth = oCanvas.width;
	var iHeight = oCanvas.height;
	var oCtx = oCanvas.getContext('2d');
	var iWidth = oCanvas.width;
	var iHeight = oCanvas.height;
	oCtx.fillStyle = "rgb(0,0,255)";
	oCtx.fillRect(currentx,currenty, 50, 50);
	document.onkeydown = keyHit;
	document.getElementById("size").selectedIndex = 4;
	document.getElementById("size").onchange = resetSize;
	document.getElementById("color").selectedIndex = 3;
	document.getElementById("color").onchange = resetColor;
	
	function showDownloadText() {
		document.getElementById("buttoncontainer").style.display = "none";
		document.getElementById("textdownload").style.display = "block";
	}

	function hideDownloadText() {
		document.getElementById("buttoncontainer").style.display = "block";
		document.getElementById("textdownload").style.display = "none";
	}

	function convertCanvas(strType) {
		if (strType == "PNG")
			var oImg = Canvas2Image.saveAsPNG(oCanvas, true);
		if (strType == "BMP")
			var oImg = Canvas2Image.saveAsBMP(oCanvas, true);
		if (strType == "JPEG")
			var oImg = Canvas2Image.saveAsJPEG(oCanvas, true);

		if (!oImg) {
			alert("Sorry, this browser is not capable of saving " + strType + " files!");
			return false;
		}

		oImg.id = "canvasimage";

		oImg.style.border = oCanvas.style.border;
		oCanvas.parentNode.replaceChild(oImg, oCanvas);

		showDownloadText();
	}

	function saveCanvas(pCanvas, strType) {
		var bRes = false;
		if (strType == "PNG")
			bRes = Canvas2Image.saveAsPNG(oCanvas);
		if (strType == "BMP")
			bRes = Canvas2Image.saveAsBMP(oCanvas);
		if (strType == "JPEG")
			bRes = Canvas2Image.saveAsJPEG(oCanvas);

		if (!bRes) {
			alert("Sorry, this browser is not capable of saving " + strType + " files!");
			return false;
		}
	}

	//document.getElementById("savepngbtn").onclick = function() {saveCanvas(oCanvas, "PNG");	}
	//document.getElementById("savebmpbtn").onclick = function() {saveCanvas(oCanvas, "BMP");	}
	//document.getElementById("savejpegbtn").onclick = function() {saveCanvas(oCanvas, "JPEG");}

	document.getElementById("convertpngbtn").onclick = function() {convertCanvas("PNG");}
	//document.getElementById("convertbmpbtn").onclick = function() {convertCanvas("BMP");}
	document.getElementById("convertjpegbtn").onclick = function() {convertCanvas("JPEG");}

	document.getElementById("resetbtn").onclick = function() {var oImg = document.getElementById("canvasimage");oImg.parentNode.replaceChild(oCanvas, oImg);
		hideDownloadText();	}
	}
Luckychap 68 Posting Pro in Training

Nice job. It would be better if there is indication of current cursor position on the canvas. Something different from background color.

anilashanbhag 0 Junior Poster in Training

I did add a tracer to keep track of the current position but yes working on adding current position.

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