add whatsnew

TODO

@@ -1,3 +1,15 @@
+- try:
+
+	john@kiwi:~/pics$ more sharp3x3.mat 
+	3 3
+	-1 -1 -1
+	-1 8 -1
+	-1 -1 -1
+	john@kiwi:~/pics$ vips convi k2.jpg x.jpg sharp3x3.con
+	VipsForeignLoad: file "sharp3x3.con" not found
+
+  works if you add 1 0 to the header line
+
 - not sure about utf8 error messages on win
 
 - strange: 

whatsnew.md

@@ -0,0 +1,131 @@
+libvips 8.4 should be out by the end of September 2016. This page introduces the main features. 
+
+## New operators
+
+There are some fun new operators. `vips_perlin()` and `vips_worley()`
+make Perlin and Worley noise. They are useful for generating
+synthetic random textures. The implementations in vips can generate images of
+any size very quickly. 
+
+## Rewritten convolution
+
+The convolution functions were the old vips7 ones with a small
+wrapper. They've now been rewritten for vips8, and the vector path has
+been completely replaced. It can be up to about 2x faster.
+
+The old vips7 vector path was based on int arithmetic, so this mask
+(a simple 3x3 average), for example:
+
+```
+3 3 9 0
+1 1 1
+1 1 1
+1 1 1
+```
+
+Would be computed as nine adds, followed by a divide by the constant 9,
+with round-to-nearest. This was obviously accurate, but dividing
+by a constant is slow.
+
+The new path first computes a fixed-point float approximation of the
+int mask. In this case it'll settle on this:
+
+```
+3 3 1 0
+3 3 3 
+3 4 4 
+4 4 4 
+```
+
+Where 3 is approximately 1/9 in 3.5 bit fixed-point, and the whole
+mask sums to 1.0 (the sum of the int mask), or 32 in 3.5 bit. 
+
+It's not possible to match each element and the sum at the same time,
+so vips uses an iterative algorithm to find the approximation that
+matches the sum exactly, matches each element as well as it can, and
+which spreads any error through the mask. In this case, the mix of 3 and 4
+is there to make the sum work. There's an error test and a fallback:
+if the maximum possible error is over 10%, it'll switch to a non-vector
+path based on exact int arithmetic. You can use `--vips-info` to see
+what path ends up being taken.
+
+Now there's a fixed-point version of the mask, vips can compute the
+convolution as 9 fused multiply-adds, followed by an add and a 5-bit shift
+to get back to the nearest int. Getting rid of the divide-by-a-constant
+gives a nice speed improvement. On my laptop with vips 8.3 and a 10k x 10k
+pixel RGB image I see:
+
+```
+$ time vips conv wtc.v x7.v avg.mat --vips-info
+real	0m1.311s
+user	0m1.376s
+sys	0m0.372s
+```
+
+With vips 8.4 it's now:
+
+```
+$ time vips convi wtc.v x8.v avg.mat --vips-info
+info: convi: using vector path
+real	0m0.774s
+user	0m0.888s
+sys	0m0.352s
+
+```
+
+The peak error is small:
+
+```
+$ vips subtract x7.v x8.v x.v
+$ vips abs x.v x2.v
+$ vips max x2.v
+11.000000
+```
+
+## Image resize
+
+`vips_resize()` has seen some good improvements. 
+
+* There's a new `centre` option which switches over to centre-convention for
+  subsampling. This makes it a much better match for ImageMagick.
+  `vipsthumbnail` uses this new option. 
+* It now does round-to-nearest when calculating image bounds. This makes it
+  much simpler to calculate a shrink factor which will produce an image of a
+  specific size.
+* A series of changes improve accuracy for the linear and cubic kernels, and
+  improve spatial accuracy.
+* It used to simply use nearest for upsampling, in line with things like PDF,
+  but this is not a good choice for many applications. It now upsizes with
+  bicubic by default. 
+
+## Unicode on Windows
+
+This is only a small thing, but the Windows build now supports Unicode
+filenames. 
+
+## File format support
+
+As usual, there are a lot of improvements to file format read and write. 
+
+* Thanks to work by Felix Bünemann, `webp` read and write supports many more 
+  options.
+* andris has improved `pdfload` so you can load many pages in a single 
+  operation.
+* Many people have worked on `dzsave` Google mode. It's now better at 
+  skipping blank tiles and supports tile overlaps. Felix Bünemann added 
+  support for compressed zip output. 
+* Henri Chain has added `radsave_buffer` to improve Radiance support.
+* TIFF files with an orientation tag should now autorotate, `tiffsave` 
+  has better jpeg compression support, and it knows about the `strip` 
+  metadata option.
+* The load-via-libMagick operator now supports IM7.
+* The GIF loader is much smarter about guessing the number of colour channels.
+* PNG save supports `strip`.
+* The SVG loader supports `svgz` compressed files thanks to Felix Bünemann.
+
+## Other
+
+Improvements to the build system, reductions in memory use, many small
+bug fixes, improvements to the C++ binding, improvements to the Python binding, 
+many small performance fixes. As usual, the ChanegLog has more detail if 
+you're interested.