The practice encourages people to think this is the way to
create a bytes.Buffer when new(bytes.Buffer) or
just var buf bytes.Buffer work fine.
(html/token.go was missing the point altogether.)
R=golang-dev, bradfitz, r
CC=golang-dev
https://golang.org/cl/5637043
Consequently, remove many package Makefiles,
and shorten the few that remain.
gomake becomes 'go tool make'.
Turn off test phases of run.bash that do not work,
flagged with $BROKEN. Future CLs will restore these,
but this seemed like a big enough CL already.
R=golang-dev, r
CC=golang-dev
https://golang.org/cl/5601057
instead of the origin.
This makes YCbCr match the other image types (e.g. RGBA, Gray) in
that an image's bounds is not restricted to the positive quadrant.
Also optimize the YCbCr draw code by hoisting some computation
outside of the loop.
benchmark old ns/op new ns/op delta
draw.BenchmarkYCbCr 2544418 2373558 -6.72%
Like https://golang.org/cl/4681044/ I don't think a gofix is
feasible. People will have to make manual changes. On the other hand,
directly manipulating YCbCr images is relatively rare, compared to
RGBA images, and if other code just uses the jpeg and draw packages
instead of messing directly with a YCbCr's []byte representations,
then things should just continue to work.
R=r
CC=golang-dev
https://golang.org/cl/5558048
The spin-off renames some types. The new names are simply better:
image.Color -> color.Color
image.ColorModel -> color.Model
image.ColorModelFunc -> color.ModelFunc
image.PalettedColorModel -> color.Palette
image.RGBAColor -> color.RGBA
image.RGBAColorModel -> color.RGBAModel
image.RGBA64Color -> color.RGBA64
image.RGBA64ColorModel -> color.RGBA64Model
(similarly for NRGBAColor, GrayColorModel, etc)
The image.ColorImage type stays in the image package, but is renamed:
image.ColorImage -> image.Uniform
The image.Image implementations (image.RGBA, image.RGBA64, image.NRGBA,
image.Alpha, etc) do not change their name, and gain a nice symmetry:
an image.RGBA is an image of color.RGBA, etc.
The image.Black, image.Opaque uniform images remain unchanged (although
their type is renamed from image.ColorImage to image.Uniform). The
corresponding color types (color.Black, color.Opaque, etc) are new.
Nothing in the image/ycbcr is renamed yet. The ycbcr.YCbCrColor and
ycbcr.YCbCrImage types will eventually migrate to color.YCbCr and
image.YCbCr, but that will be a separate CL.
R=r, bsiegert
CC=golang-dev
https://golang.org/cl/5132048
of the origin.
image/png and image/jpeg benchmarks show no significant changes.
The image/draw changes suggest to me that making a gofix for this is not
feasible. People are just going to have to make manual fixes.
R=r
CC=golang-dev
https://golang.org/cl/4681044
writing the idct result directly to the image buffer instead of
storing it in an intermediate d.blocks field.
Writing to d.blocks was necessary when decoding to an image.RGBA image,
but now that we decode to a ycbcr.YCbCr we can write each component
directly to the image buffer.
Crude "time ./6.out" scores to decode a specific 2592x1944 JPEG 20
times show a 16% speed-up:
BEFORE
user 0m10.410s
user 0m10.400s
user 0m10.480s
user 0m10.480s
user 0m10.460s
AFTER
user 0m9.050s
user 0m9.050s
user 0m9.050s
user 0m9.070s
user 0m9.020s
R=r
CC=golang-dev
https://golang.org/cl/4523052
Avoids image.At(), color.RGBA(), opposing 8 bit shifts,
and min function calls in a loop. Not as pretty as before,
but the pure version is still there to revert back to
later if/when the compiler gets better.
before (best of 5)
jpeg.BenchmarkEncodeRGBOpaque 50 64781360 ns/op 18.97 MB/s
after (best of 5)
jpeg.BenchmarkEncodeRGBOpaque 50 42044300 ns/op 29.23 MB/s
(benchmarked on an HP z600; 16 core Xeon E5520 @ 2.27Ghz)
R=r, r2, nigeltao
CC=golang-dev
https://golang.org/cl/4433088
This is not a complete JPEG implementation (e.g. it does not handle
progressive JPEGs or restart markers), but I was able to take a photo
with my phone, and view the resultant JPEG in pure Go.
The decoder is simple, but slow. The Huffman decoder in particular
should be easily improvable, but optimization is left to future
changelists. Being able to inline functions in the inner loop should
also help performance.
The output is not pixel-for-pixel identical to libjpeg, although
identical behavior isn't necessarily a goal, since JPEG is a lossy
codec. There are at least two reasons for the discrepancy.
First, the inverse DCT algorithm used is the same as Plan9's
src/cmd/jpg, which has different rounding errors from libjpeg's
default IDCT implementation. Note that libjpeg actually has three
different IDCT implementations: one floating point, and two fixed
point. Out of those four, Plan9's seemed the simplest to understand,
partly because it has no #ifdef's or C macros.
Second, for 4:2:2 or 4:2:0 chroma sampling, this implementation does
nearest neighbor upsampling, compared to libjpeg's triangle filter
(e.g. see h2v1_fancy_upsample in jdsample.c).
The difference from the first reason is typically zero, but sometimes
1 (out of 256) in YCbCr space, or double that in RGB space. The
difference from the second reason can be as large as 8/256 in YCbCr
space, in regions of steep chroma gradients. Informal eyeballing
suggests that the net difference is typically imperceptible, though.
R=r
CC=golang-dev, rsc
https://golang.org/cl/164056
