function checkSource()

in seriously.js [542:607]
54 lines of code
14 McCabe index (conditional complexity)

	function checkSource(source) {
		var element, canvas, ctx, texture;

		//todo: don't need to create a new array every time we do this
		element = getElement(source, ['img', 'canvas', 'video']);
		if (!element) {
			return false;
		}

		canvas = document.createElement('canvas');
		if (!canvas) {
			Seriously.logger.warn('Browser does not support canvas or Seriously.js');
			return false;
		}

		if (element.naturalWidth === 0 && element.tagName === 'IMG') {
			Seriously.logger.warn('Image not loaded');
			return false;
		}

		if (element.readyState === 0 && element.videoWidth === 0 && element.tagName === 'VIDEO') {
			Seriously.logger.warn('Video not loaded');
			return false;
		}

		ctx = getTestContext();
		if (ctx) {
			texture = ctx.createTexture();
			if (!texture) {
				Seriously.logger.error('Test WebGL context has been lost');
			}

			ctx.bindTexture(ctx.TEXTURE_2D, texture);

			try {
				ctx.texImage2D(ctx.TEXTURE_2D, 0, ctx.RGBA, ctx.RGBA, ctx.UNSIGNED_BYTE, element);
			} catch (textureError) {
				if (textureError.code === window.DOMException.SECURITY_ERR) {
					Seriously.logger.log('Unable to access cross-domain image');
				} else {
					Seriously.logger.error('Error storing image to texture: ' + textureError.message);
				}
				ctx.deleteTexture(texture);
				return false;
			}
			ctx.deleteTexture(texture);
		} else {
			ctx = canvas.getContext('2d');
			try {
				ctx.drawImage(element, 0, 0);
				ctx.getImageData(0, 0, 1, 1);
			} catch (drawImageError) {
				if (drawImageError.code === window.DOMException.SECURITY_ERR) {
					Seriously.logger.log('Unable to access cross-domain image');
				} else {
					Seriously.logger.error('Error drawing image to canvas: ' + drawImageError.message);
				}
				return false;
			}
		}

		// This method will return a false positive for resources that aren't
		// actually images or haven't loaded yet

		return true;
	}