Ticket #64 (closed defect: fixed)

Opened 12 months ago

Last modified 4 months ago

im.blend treats transparency on/off

Reported by: gravitystorm Owned by: artem
Priority: critical (top) Milestone:
Component: Core Library Version:
Severity: Normal Keywords:
Cc: Patch Needs Improvement: no
Needs Docmentation: no Has Patch?: yes
Design Decision Needed: no

Description

(originally reported via email to Artem)

im.blend doesn't take alpha-transparency into account properly when using an image with a transparent background. Each pixel is assumed to be either fully transparent or fully opaque, which leads to jagged outlines.

The attached blend.png shows a transparent layer containing circles blended onto a white background. Notice that the circles are fine when overlapping, but jagged where the layers have been blended.

Patch follows.

Attachments

blend.png (12.7 kB) - added by gravitystorm 12 months ago.
shows jagged outline due to alpha-transparency blend failure
mapnik-alpha.patch (1.4 kB) - added by gravitystorm 12 months ago.
patch to give correct behaviour

Change History

Changed 12 months ago by gravitystorm

shows jagged outline due to alpha-transparency blend failure

Changed 12 months ago by gravitystorm

patch to give correct behaviour

Changed 12 months ago by dave

  • status changed from new to closed
  • resolution set to fixed

Patch committed in r601

Changed 4 months ago by springmeyer

  • priority set to critical (top)
  • has_patch set
  • patch_need_improvement unset
  • need_documentation unset
  • design_decision_needed unset
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