https://issues.apache.org/bugzilla/show_bug.cgi?id=48274
Summary: HSSFPalette.findSimilarColor treats 0 and 255 as
adjacent
Product: POI
Version: unspecified
Platform: All
OS/Version: All
Status: NEW
Severity: normal
Priority: P2
Component: HSSF
AssignedTo: [email protected]
ReportedBy: [email protected]
Created an attachment (id=24605)
--> (https://issues.apache.org/bugzilla/attachment.cgi?id=24605)
patch for HSSFPalette.java and TestHSSFPalette.java
HSSFPalette.findSimilarColor considers a color value of 0 to be closer than 255
it is to 127. Thus, for example,
HSSFWorkbook workbook = new HSSFWorkbook();
HSSFPalette palette = workbook.getCustomPalette();
HSSFColor color = palette.findSimilarColor(0,102,255);
short[] rgb = color.getTriplet();
System.out.println(java.util.Arrays.toString(rgb));
prints "[255,102,0]". The input color is not unlike turquoise, but the output
color is a light red!
The reason findSimilarColor behaves this way is because it implements the
Manhattan distance in byte space. byte is signed, and thus 255 is really -1,
which is adjacent to 0.
A patch is enclosed which first converts the bytes to positive integers so that
255 is maximally far from 0. Then the above example returns [0,102,204] which
is much closer to the original [0,102,255]. The patch also includes additional
tests for TestHSSFPalette.
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