Bug 18821

Summary:

Canvas putImageData incorrect when data has alpha

Product:

WebKit

Reporter:

Philip Taylor <excors>

Component:

DOM

Assignee:

Dave Hyatt <hyatt>

Status:

RESOLVED FIXED

Severity:

Normal

Priority:

Version:

528+ (Nightly build)

Hardware:

OS:

Windows Vista

URL:

http://philip.html5.org/tests/canvas/misc/alpha-putimagedata.html

Attachments:

Description	Flags
Fix bugs in the loops of both get and putImageData	hyatt: review-
Fix bugs in the loops of both get and putImageData	eric: review+
Patch to fix the bug	eric: review+

Description Philip Taylor 2008-04-30 18:31:11 PDT

See test case in URL. It draws a very-transparent red column on the left, then fills the rest of the canvas with slightly-transparent green, then calls putImageData(getImageData(...), ...) which should have no effect.

Expected output: alert box saying "0,255,0,254" (or maybe 253), alert box saying "0,255,0,254" (or maybe 253), green canvas.

Actual output: alert box saying "0,255,0,253", alert box saying "255,0,0,253", red canvas.

Tested on Windows r32574.

Comment 1 Dave Hyatt 2008-05-01 11:50:41 PDT

Created attachment 20914 [details]
Fix bugs in the loops of both get and putImageData

Comment 2 Dave Hyatt 2008-05-01 11:51:57 PDT

Created attachment 20915 [details]
Fix bugs in the loops of both get and putImageData

Comment 3 Eric Seidel (no email) 2008-05-01 19:41:15 PDT

Comment on attachment 20915 [details]
Fix bugs in the loops of both get and putImageData

Needs a test case and changelog when you land.  Otherwise fine.

Comment 4 Dave Hyatt 2008-05-05 11:19:38 PDT

Created attachment 20971 [details]
Patch to fix the bug

Comment 5 Eric Seidel (no email) 2008-05-05 11:27:45 PDT

Comment on attachment 20971 [details]
Patch to fix the bug

Looks saner.  Still needs a ChangeLog when landing.

Comment 6 Dave Hyatt 2008-05-05 11:29:58 PDT

Fixed in r32878.