231974 - scaled png with alpha mask has its background scaled too

Status: RESOLVED DUPLICATE of bug 150881

(Core :: Layout: Images, Video, and HTML Frames, defect)

Description

[Tiago Freire]

User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.5) Gecko/20031007
Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.5) Gecko/20031007

if I have, for example a div1 with some text, with another div2 on top of it,
and on div2 I put a png image, 20x20 pixels, with an alpha mask. I should see
through and be able to read text. If I set a style scaling the image for 40
pixels wide , or 80, or whatever, the background is scaled too, but in a weird
way. for example if I stretch the image 4 times horizontally, each 4 pixel-wide
column which corresponds to a single pixel line unstretched looks for one pixel
below it , and stretches it. But, while examining the screenshot, we can also
notice that in some cases, when we have several colors in the 4pixel wide column
in the same line, the stretched pixel gets dark or black. 



Reproducible: Always

Steps to Reproduce:
1.
2.
3.




Mozilla 1.5
I wanted to use an alpha masked png to add a gradient to a div and change the
div background using styles for some effects, but it seems that it will not work
on a stretched image. this bug seems to be uncovered only when the image is
stretched.

Comment 1

[Tiago Freire]

Attachment: screenshot describing bug

The screenshot has only 139 colors, so I reduced its size. it is scaled 4 times
to better see the pixels, I have also put a grid.

Comment 2

[Tiago Freire]

Attachment: html used to create testcase

html used to create testcase

Comment 3

[Tiago Freire]

Attachment: image for testcase

Comment 4

[Tiago Freire]

Attachment: THE image with alpha channel

Comment 5

[Tiago Freire]

the testcase features the image at its normal size, then stretched 2x
horizontally, then 3x, then 4x.

Comment 6

[tor]

This should be fixed by the checkin for 150881, and I can't replicate it
on a current build.  Try downloading mozilla 1.6 or a nightly and see if
you still see the problem.

Comment 7

[Tiago Freire]

YES, it is fixed on Mozilla 1.6. Great!

Comment 8

[tor]

Thanks for checking.  Resolving bug as duplicate.


*** This bug has been marked as a duplicate of 150881 ***