Hi Jim,
I performed performance analysis with white image so that all conditions are
checked in the new branch added. There is no major difference in time taken
before and after change. For each input I have tested time taken for
drawImage() API to convert from every format to Byte indexed type. For every
unique conversion test is run for 100 times. Please find the details:
Input
type
Min
before change
(ns)
Min
after change
(ns)
Max
before change
(ns)
Max
after change
(ns)
Average
before change
(ns)
Average
after
change
(ns)
INT_RGB
523437
481491
1230724
1270440
789452
666144
INT_ARGB
500232
493986
12406307
1308816
793384
654015
INT_ARGB_PRE
500233
492201
1037057
981277
710250
699214
INT_BGR
537716
562706
1446703
2046001
862377
863256
3BYTE_BGR
483275
481045
1181638
1384676
651427
580961
4BYTE_ABGR
544410
499786
1292305
968783
690106
683881
4BYTE_ABGR_PRE
504249
505588
1680086
1216445
756101
687750
USHORT_565_RGB
507818
505588
978153
1346746
652908
655782
USHORT_555_RGB
510496
509604
952272
1162004
650418
670811
BYTE_GRAY
481491
478367
1140585
1799231
691160
583250
USHORT_GRAY
506927
507373
1375751
1255267
728202
646902
BYTE_BINARY
541733
496217
1083466
959411
730527
728461
The changes are tested with plain images having primary colors like RED, GREEN,
BLUE, BLACK and WHITE.
Thanks,
Jay
-----Original Message-----
From: Jim Graham
Sent: Friday, February 12, 2016 4:05 AM
To: Jayathirth D V; 2d-dev@openjdk.java.net; Philip Race; Prasanta Sadhukhan
Subject: Re: [OpenJDK 2D-Dev] Review Request for JDK-7116979 : Unexpected pixel
colour when converting images to TYPE_BYTE_INDEXED
Hi Jayathirth,
Did you do any performance analysis of this change? You are adding 6 tests and
multiple branches to per-pixel code.
The effectiveness of this technique depends on the colormap that we have set
up. For the BufferedImage.TYPE_INDEXED constructor we produce a fairly nice
colormap, but if someone creates a custom colormap then the colors could be
anything. We create a decent inversion for just about any colormap, but that
doesn't mean that using only "the best match for solid red" will produce a
better result for a dithered approximation for red. It is true that if there
is a really good match for red then we should just use that, but if there are
no direct matches for red then we may choose to paint a red region with solid
orange even though there is another color in the colormap that when mixed with
orange approximates a red tone better. For example, if a colormap contains no
pure red, but
contains:
240, 20, 0
240, 0, 20
(I'm not sure if 20 is within our current error deltas that we use for
dithering, but this is an example not a test case.)
Then using one of these alone might skew the color towards orange or purple.
Using both together in a dither pattern might keep the overall hue impression
as red, but with a small amount of noise in its saturation.
What types of colormaps was this tested with?
...jim
On 2/11/16 6:37 AM, Jayathirth D V wrote:
> Hi,
>
> _Please review the following fix in JDK9:_
>
> __
>
> Bug : https://bugs.openjdk.java.net/browse/JDK-7116979
>
> Webrev : http://cr.openjdk.java.net/~jdv/7116979/webrev.00/
>
> Issue : When Image containing black pixels are converted from any
> format to Byte Indexed format some of the pixels are not black. They
> are following pattern similar to dithering.
>
> Root cause : When we convert any format type to ByteIndexed we are
> adding Error delta values to R,G,B components using dithering indices.
> This is causing some pixels values to not point to proper index in
> color table.
>
> Solution : There is no need to add error delta for primary colors
> containing basic values in R,G,B components. Exclude such pixels from
> delta addition.
>
> Thanks,
>
> Jay
>
