Bug 192807 – An unexpected 1px line appears when using context.drawImage() method to show a specified part of a JPEG file

• Component: Canvas
• Status: RESOLVED MOVED

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.

Created attachment 357546 [details]
a html file used for this test.

Created attachment 357548 [details]
test files

[Radar WebKit Bug Importer]

<rdar://problem/46926648>

[Simon Fraser (smfr)]

This appears to be a bug in the underlying graphics framework, not WebKit.

[Simon Fraser (smfr)]

This will be fixed in a future iOS version.