406479 - <canvas> repeated low-opacity fills have no effect

Status: RESOLVED INVALID

(Core :: Graphics: Canvas2D, defect)

Description

[Ilmari Heikkinen]

User-Agent:       Mozilla/5.0 (X11; U; Linux i686; fi; rv:1.8.1.9) Gecko/20071025 Firefox/2.0.0.9
Build Identifier: Mozilla/5.0 (X11; U; Linux i686; fi; rv:1.8.1.9) Gecko/20071025 Firefox/2.0.0.9

Filling an area of rgba(132, 132, 132, 1.0)-pixels with rgba(128,128,128, 0.1) has no effect.


Reproducible: Always

Steps to Reproduce:
1. fill canvas with a color
2. repeatedly fill canvas with a second, low-opacity color

Actual Results:  
The filled area never reaches the second color.

Expected Results:  
The area should eventually turn to the fully opaque version of the second color.

Comment 1

[Ilmari Heikkinen]

Attachment: testcase

Comment 2

[Joe Drew (not getting mail)]

The filling does have an effect, despite the reporter's summary. The complaint is that the canvas never reaches a uniform grey, but as far as I can tell the canvas is doing exactly what I would expect an OVER operation to do, mathematically if not intuitively.

Feel free to reopen if I'm way off-base.