These forums are currently read-only due to receiving more spam than actual discussion. Sorry.

It is currently Sat Dec 02, 2017 4:24 pm Advanced search

Canvas and Image problem (when using stroke / lines)

If you are stuck or have questions regarding HTML or other Web technologies, ask your questions here. No question too dumb!

Canvas and Image problem (when using stroke / lines)

Postby driv3l » Mon May 23, 2011 5:28 pm

Hi,

I've been struggling with this issue for a while now... I've looked at the Canvas tutorials and specs muliple times, but cannot find a solution to my problem.

I am putting an image directly onto the canvas using ctx.drawImage(img, 0, 0, width, height, scalewidth, scaleheight). I have already drawn rectangles and / or lines onto the canvas using strokeRect and moveTo and lineTo.

The behavior I want is for the image I draw to hide / overwrite any lines drawn under it. However, this does not seem to happen. I consistently get the lines showing over the image I am drawing. The image is fully opaque (no transparency set).

I have tried setting the globalCompositeOperation to "copy" whenever I draw the image, but this has no effect.

I have also tried alternate approaches like doing a clearRect() in the location I am planning on drawing the image, however, when I do a clearRect() and then do a drawImage(), when I run it in the browser, I can see the image being drawn, but then it is immediately cleared (almost like drawImage is rendering before clearRect).

I am totally flustered by how to get this working properly.

Any help would be greatly appreciated!!!

Btw, I'm testing this on Chrome (tried it on IE and Firefox as well and get the same behavior).

Thanks!
driv3l
<h6>
 
Posts: 1
Joined: Mon May 23, 2011 5:19 pm

Re: Canvas and Image problem (when using stroke / lines)

Postby zcorpan » Tue May 24, 2011 9:47 am

Would be helpful if you showed us the code :)
zcorpan
<article>
 
Posts: 807
Joined: Tue Feb 06, 2007 8:29 pm
Location: Sweden


Return to Help & Advice

Who is online

Users browsing this forum: No registered users and 0 guests