all: fix some comments

Change-Id: I13de571f2169ec8adc42dc69dbb45c3b2fc57371
Reviewed-on: https://go-review.googlesource.com/c/image/+/713121
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Sean Liao <sean@liao.dev>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Sean Liao <sean@liao.dev>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>

 font/sfnt/kern_test.go | 2 +-
 tiff/reader.go         | 2 +-
 vector/vector.go       | 4 ++--
 vp8/predfunc.go        | 2 +-
 vp8/reconstruct.go     | 2 +-
 5 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/font/sfnt/kern_test.go b/font/sfnt/kern_test.go
index 163dac7..76c9c33 100644
--- a/font/sfnt/kern_test.go
+++ b/font/sfnt/kern_test.go
@@ -14,7 +14,7 @@ glyph pairs.
 These tests only check if there are no errors during kerning. Tests of actual
 kerning values are in proprietary_test.go.
 
-Note: CJK fonts can contain billions of posible kerning pairs. Testing for
+Note: CJK fonts can contain billions of possible kerning pairs. Testing for
 these fonts stops after -bulkMaxKernPairs.
 
 To opt-in:
diff --git a/tiff/reader.go b/tiff/reader.go
index 1b8fcb8..4c1de45 100644
--- a/tiff/reader.go
+++ b/tiff/reader.go
@@ -721,7 +721,7 @@ func Decode(r io.Reader) (img image.Image, err error) {
 			switch d.firstVal(tCompression) {
 
 			// According to the spec, Compression does not have a default value,
-			// but some tools interpret a missing Compression value as none so we do
+			// but some tools interpret a missing Compression value as none, so we do
 			// the same.
 			case cNone, 0:
 				if b, ok := d.r.(*buffer); ok {
diff --git a/vector/vector.go b/vector/vector.go
index 7b8ca98..8be770e 100644
--- a/vector/vector.go
+++ b/vector/vector.go
@@ -34,7 +34,7 @@ import (
 // Both implementations of line segmentation rasterization (see raster_fixed.go
 // and raster_floating.go) implement the same algorithm (in ideal, infinite
 // precision math) but they perform differently in practice. The fixed point
-// math version is roughtly 1.25x faster (on GOARCH=amd64) on the benchmarks,
+// math version is roughly 1.25x faster (on GOARCH=amd64) on the benchmarks,
 // but at sufficiently large scales, the computations will overflow and hence
 // show rendering artifacts. The floating point math version has more
 // consistent quality over larger scales, but it is significantly slower.
@@ -251,7 +251,7 @@ func (z *Rasterizer) CubeTo(bx, by, cx, cy, dx, dy float32) {
 // The reason for the subdivision by n is that I expect the "flatness"
 // computation to be semi-expensive (it's done once rather than on each
 // potential subdivision) and also because you'll often get fewer subdivisions.
-// Taking a circular arc as a simplifying assumption (ie a spherical cow),
+// Taking a circular arc as a simplifying assumption (i.e., a spherical cow),
 // where I get n, a recursive approach would get 2^⌈lg n⌉, which, if I haven't
 // made any horrible mistakes, is expected to be 33% more in the limit.
 func devSquared(ax, ay, bx, by, cx, cy float32) float32 {
diff --git a/vp8/predfunc.go b/vp8/predfunc.go
index f899958..bd554ae 100644
--- a/vp8/predfunc.go
+++ b/vp8/predfunc.go
@@ -4,7 +4,7 @@
 
 package vp8
 
-// This file implements the predicition functions, as specified in chapter 12.
+// This file implements the prediction functions, as specified in chapter 12.
 //
 // For each macroblock (of 1x16x16 luma and 2x8x8 chroma coefficients), the
 // luma values are either predicted as one large 16x16 region or 16 separate
diff --git a/vp8/reconstruct.go b/vp8/reconstruct.go
index c1cc4b5..67e4c36 100644
--- a/vp8/reconstruct.go
+++ b/vp8/reconstruct.go
@@ -178,7 +178,7 @@ var unpack = [16][4]uint8{
 var (
 	// The mapping from 4x4 region position to band is specified in section 13.3.
 	bands = [17]uint8{0, 1, 2, 3, 6, 4, 5, 6, 6, 6, 6, 6, 6, 6, 6, 7, 0}
-	// Category probabilties are specified in section 13.2.
+	// Category probabilities are specified in section 13.2.
 	// Decoding categories 1 and 2 are done inline.
 	cat3456 = [4][12]uint8{
 		{173, 148, 140, 0, 0, 0, 0, 0, 0, 0, 0, 0},