[OpenJDK 2D-Dev]  request for review: 8041465: BMPImageReader read error using ImageReadParam with set sourceRectangle
philip.race at oracle.com
Wed Sep 3 19:20:57 UTC 2014
On 9/3/2014 5:23 AM, Andrew Brygin wrote:
> could you please review a fix for CR 8041465?
> Bug: https://bugs.openjdk.java.net/browse/JDK-8041465
> Webrev: http://cr.openjdk.java.net/~bae/8041465/9/webrev.00/
> The problem happens if we perform multiple read operations from
> a source which is set only once. For instance, we can try to read
> image in several tiles.
> The root case of the problem is that we set stream position
> to the start of raster data only once: when we complete
> the processing of BMP header. A peculiarity of BMP format
> is that raster data can be stored in reverse order, so if we
> request few leading scanlines first, then we skip rest of raster
> data, and subsequent read command does not copy anything to the
> destination buffer, because we never re-set the stream position
> to the start of bitmap.
> Suggested fix just saves the bitmap's start postilion and seeks
> the stream to to it each time when we read image. This change
> makes the BMP reader behavior exactly same as other standard plugin
> Supplied regression test demonstrates the problem.
> Please take a look.
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