Bug 192807

Summary: An unexpected 1px line appears when using context.drawImage() method to show a specified part of a JPEG file
Product: WebKit Reporter: nishiyama.satomi
Component: CanvasAssignee: Nobody <webkit-unassigned>
Status: RESOLVED MOVED    
Severity: Normal CC: baba, dino, harayama.shouichi, sabouhallawa, simon.fraser, webkit-bug-importer
Priority: P2 Keywords: InRadar
Version: Safari 12   
Hardware: iPhone / iPad   
OS: iOS 12   
Attachments:
Description Flags
an unexpected 1px red line on a JPEG file.
none
a html file used for this test.
none
test files none

Description nishiyama.satomi 2018-12-18 00:10:18 PST
Created attachment 357545 [details]
an unexpected 1px red line on 
a JPEG file.

Hello,

I found an issue with JPEG drawing on iOS 12 devices.
An unexpected 1px line appears on a image when I use context.drawImage() method of html to show a specified part of a JPEG file.
It doesn't occur when using iOS12 simulators or iOS11 devices.

[Steps to reproduce the problem]
1. Open 'index.html' on Safari using iPhone/iPad on iOS12.
  This html file shows a specified part of each following file.
       'test.jpg',
       'test.png',
       'test.jp2',
       'test.gif'
2. An unexpected 1px red line appears on 'test.jpg' image. No problems with the other files, though.

[What is the expected behavior?]
No unexpected lines appear on a JPEG image like the other file formats ( : png, jp2, gif).

[What went wrong?]
An unexpected 1px red line appears on a JPEG image.

[Is it a problem with a plugin?]
N/A

[Did this work before?]
N/A

[Does this work in other browsers?]
Yes

Thank you.
Comment 1 nishiyama.satomi 2018-12-18 00:13:15 PST
Created attachment 357546 [details]
a html file used for this test.
Comment 2 nishiyama.satomi 2018-12-18 00:18:58 PST
Created attachment 357548 [details]
test files
Comment 3 Radar WebKit Bug Importer 2018-12-23 17:43:54 PST
<rdar://problem/46926648>
Comment 4 Simon Fraser (smfr) 2019-01-02 11:21:45 PST
This appears to be a bug in the underlying graphics framework, not WebKit.
Comment 5 Simon Fraser (smfr) 2019-01-10 14:00:20 PST
This will be fixed in a future iOS version.