[Bug classpath/37126] New: gnu.javax.imageio.bmp.DecodeRGB24.decode() do not decode correcxtly some colors

[mathieu dot baron at gmail dot com]

gnu.javax.imageio.bmp.DecodeRGB24.decode() do not decode some pixels correctly.

Current code:
    for(int x=0;x<w;x++)
        data[x + y*w] = ((scanline[x*3]) + // Red
            ((scanline[x*3+1] << 8)) +     // Green
            ((scanline[x*3+2] << 16)));    // Blue

Example:
    Fuchsia color (0x00FF00FF)
        Red   --> 0xFF --> (Byte) 0xFF --> -1
        Green --> 0x00 --> (Byte) 0x00 --> 0
        Blue  --> 0xFF --> (Byte) 0xFF --> -1

    Current Encode Color Algorithm:
        Red + (Green << 8) + (Blue << 16)
         -1 +           0  +      -65536  ==  -65537 = 0xFFFFFEFF

    The encoded color is not the expected one:
        0xFFFFFEFF != (0x00FF00FF) Fuchsia

Proposed solution:
    1. Use a mask to isolate byte color values
    2. Use the OR bitwise operator to merge pixel's RGB values

    Example:
        for(int x=0;x<w;x++)
            data[x + y*w] = ((scanline[x*3] & 0x000000FF) | // Red
                ((scanline[x*3+1] << 8) & 0x0000FF00) |     // Green
                ((scanline[x*3+2] << 16) & 0x00FF0000));    // Blue


-- 
           Summary: gnu.javax.imageio.bmp.DecodeRGB24.decode() do not decode
                    correcxtly some colors
           Product: classpath
           Version: 0.97.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: classpath
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: mathieu dot baron at gmail dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37126