GeoServer

Translucent colors in input + solid background not properly handled by the direct render path

Details

  • Type: Bug Bug
  • Status: Closed Closed
  • Priority: Major Major
  • Resolution: Fixed
  • Affects Version/s: 2.1-RC1
  • Fix Version/s: 2.1-RC2
  • Component/s: None
  • Labels:
    None
  • Number of attachments :
    3

Description

Cascading topp:states after solving GEOS-4337 still shows issues when then image had translucent, but not fully transparent, pixels.

Attached two images, "original.jpeg" is the image produced by GeoServer without cascading, in JPEG format, with no transparency, whilst "cascaded.jpeg" is the one we get from cascading.

  1. Text File
    GEOS-4360.patch
    06/Feb/11 9:38 AM
    5 kB
    Andrea Aime
  1. cascaded.jpeg
    22 kB
    05/Feb/11 12:27 PM
  2. original.jpeg
    21 kB
    05/Feb/11 12:17 PM

Activity

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Andrea Aime added a comment -

The last mosaic operation takes the fully transparent pixels and turns them into solid white. However the colors that were translucent are left as they are.
When the last operation shaves off the alpha channel the transparency information is lost and the color becomes solid.
We need an operation that actually blends the translucent colors with the background one before removing the alpha channel.

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Andrea Aime added a comment - The last mosaic operation takes the fully transparent pixels and turns them into solid white. However the colors that were translucent are left as they are. When the last operation shaves off the alpha channel the transparency information is lost and the color becomes solid. We need an operation that actually blends the translucent colors with the background one before removing the alpha channel.
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Andrea Aime added a comment -

It seems to me the "composite" operation does the trick, but it's a heavy one, so it should be used in alternative to Mosaic only if the input image is RGBA but the output is RGB (and in fact only if the input image has any translucent pixels, but to know that we'd have to run a histogram on the input image alpha channel and check if there is any pixel with values other than 0 and 255... probably not worth the pain?)

Show
Andrea Aime added a comment - It seems to me the "composite" operation does the trick, but it's a heavy one, so it should be used in alternative to Mosaic only if the input image is RGBA but the output is RGB (and in fact only if the input image has any translucent pixels, but to know that we'd have to run a histogram on the input image alpha channel and check if there is any pixel with values other than 0 and 255... probably not worth the pain?)
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Andrea Aime added a comment -

The attached patch seems to be working fine in all cases I've tried it, and also makes sure there is no color inversion without the need to apply any other change.
I have the impression it does "composite" more often than necessary but also removes the usage of mosaic and crop in some cases. The performance by the naked eye still seems quite good.

Show
Andrea Aime added a comment - The attached patch seems to be working fine in all cases I've tried it, and also makes sure there is no color inversion without the need to apply any other change. I have the impression it does "composite" more often than necessary but also removes the usage of mosaic and crop in some cases. The performance by the naked eye still seems quite good.
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Andrea Aime added a comment -

Fixed on 2.1.x and trunk

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Andrea Aime added a comment - Fixed on 2.1.x and trunk
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Andrea Aime added a comment -

Bulk closing all resolved issue that have not gotten any more feedback or comment in the last month

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Andrea Aime added a comment - Bulk closing all resolved issue that have not gotten any more feedback or comment in the last month

People

  • Assignee:
    Simone Giannecchini
    Reporter:
    Andrea Aime
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Dates

  • Created:
    Updated:
    Resolved: