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This test ensures that getImageData works correctly.
<div id="log"></div>
<script>
if (window.testRunner)
testRunner.dumpAsText();
var canvas = document.createElement("canvas");
canvas.width = 200;
canvas.height = 200;
var context = canvas.getContext("2d");
function log(msg){
document.getElementById("log").innerHTML += msg + "<br/>";
}
function dataToArray(data) {
var result = new Array(data.length)
for (var i = 0; i < data.length; i++)
result[i] = data[i];
return result;
}
function getPixel(ctx, x, y) {
var data = ctx.getImageData(x,y,1,1);
if (!data) // getImageData failed, which should never happen
return [-1,-1,-1,-1];
return dataToArray(data.data);
}
function pixelShouldBe(ctx, x, y, colour) {
var ctxColour = getPixel(ctx, x, y);
var correct = true;
for (var i = 0; i < 4; i++)
if (colour[i] != ctxColour[i]) {
correct = false;
break;
}
if (correct)
log("PASS: pixel at ("+[x,y]+") was ["+colour+"]");
else
log("FAIL: pixel at ("+[x,y]+") was ["+ctxColour+"], expected ["+colour+"]");
}
if (!context.setFillColor)
context.setFillColor = function(r,g,b,a) {
this.fillStyle = "rgba("+[Math.round(r*255),Math.round(g*255),Math.round(b*255),Math.round(a*255)]+")"
}
// Check that getImageData is return the data for the right portion of the image
for(var x = 0; x < 100; x+=4) {
context.setFillColor(0, x/96, 0, 1);
context.fillRect(x,0,1,1);
pixelShouldBe(context, x, 0, [0, Math.round(255*x/96), 0, 255]);
}
// Check rgba ordering
context.clearRect(0,0,100,100);
context.setFillColor(0.25, 0.5, 0.75, 1);
context.fillRect(5,5,1,1);
pixelShouldBe(context, 5, 5, [Math.round(0.25*255), Math.round(0.5*255), Math.round(0.75*255), 255]);
// Make sure we return correct values for the row
for (var i = 0; i < 100; i++) {
context.fillStyle = "rgba("+[0, i, 0, 1]+")";
context.fillRect(i, 10, 1, 1);
}
var rowImageData = context.getImageData(0, 10, 100, 1).data;
var rowCheck = true;
for (var i = 0; i < 100; i++) {
if (rowImageData[i * 4 + 1] != i) {
rowCheck = false;
break;
}
}
if (!rowCheck)
log("FAIL: Did not correctly retrieve every pixel in a row");
else
log("PASS: Correctly retrieved every pixel in a row");
// Check that we return transparent black for regions outside the canvas proper
context.fillStyle = "rgba(255,255,255,255)";
context.fillRect(198, 5, 4, 1); // final 2 pixels horizontally should be clipped
var content = dataToArray(context.getImageData(198, 5, 4, 1).data);
var expected = [255,255,255,255,255,255,255,255,
0,0,0,0,0,0,0,0];
var matched = true;
for (var i = 0; i < 16; i++)
if (content[i] != expected[i]) {
matched = false;
break;
}
if (matched)
log("PASS: Correct data for content outside canvas bounds");
else
log("FAIL: Did not get correct data for content outside canvas bounds: "+content);
</script>
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