image: use built-in clear to simplify code

Change-Id: Id34936a115baaf61e4268582c6d9a2027494c385
GitHub-Last-Rev: 5fe455b7d24e3e3b871c8999c5bb534f3e1e3ab5
GitHub-Pull-Request: golang/go#66244
Reviewed-on: https://go-review.googlesource.com/c/go/+/570555
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Auto-Submit: Keith Randall <khr@golang.org>

diff --git a/src/image/draw/draw.go b/src/image/draw/draw.go
index 1b7e90f249f45fc418efa66c5b998175594df06e..50c0b918f4fd176c682cf600134495a9f5fbd0ea 100644 (file)
--- a/src/image/draw/draw.go
+++ b/src/image/draw/draw.go
@@ -1078,9 +1078,7 @@ func drawPaletted(dst Image, r image.Rectangle, src image.Image, sp image.Point,
                // Recycle the quantization error buffers.
                if floydSteinberg {
                        quantErrorCurr, quantErrorNext = quantErrorNext, quantErrorCurr
-                       for i := range quantErrorNext {
-                               quantErrorNext[i] = [4]int32{}
-                       }
+                       clear(quantErrorNext)
                }
        }
 }

diff --git a/src/image/gif/reader.go b/src/image/gif/reader.go
index b4ea4fdea1f3e0c5909db452e318a9a849b44e36..8d6faf87a3cf861e47c75f730db47183ccaee968 100644 (file)
--- a/src/image/gif/reader.go
+++ b/src/image/gif/reader.go
@@ -406,10 +406,8 @@ func (d *decoder) readImageDescriptor(keepAllFrames bool) error {
                        // seem OK with this, so we enlarge the palette with
                        // transparent colors. See golang.org/issue/15059.
                        p := make(color.Palette, ti+1)
-                       copy(p, m.Palette)
-                       for i := len(m.Palette); i < len(p); i++ {
-                               p[i] = color.RGBA{}
-                       }
+                       i := copy(p, m.Palette)
+                       clear(p[i:])
                        m.Palette = p
                }
        }

diff --git a/src/image/gif/writer.go b/src/image/gif/writer.go
index 7220446de5ebf308f38b94faefd49426ce6c3c99..0da47f3e35b966d504dc4bc5a683dca9050b61a6 100644 (file)
--- a/src/image/gif/writer.go
+++ b/src/image/gif/writer.go
@@ -220,10 +220,7 @@ func encodeColorTable(dst []byte, p color.Palette, size int) (int, error) {
        n := log2Lookup[size]
        if n > len(p) {
                // Pad with black.
-               fill := dst[3*len(p) : 3*n]
-               for i := range fill {
-                       fill[i] = 0
-               }
+               clear(dst[3*len(p) : 3*n])
        }
        return 3 * n, nil
 }

diff --git a/src/image/jpeg/huffman.go b/src/image/jpeg/huffman.go
index 72444369ab3e112d55bf678254a7305dab59ef12..0b81fbae9663b7b8555d4296d8de552065a94a08 100644 (file)
--- a/src/image/jpeg/huffman.go
+++ b/src/image/jpeg/huffman.go
@@ -131,9 +131,7 @@ func (d *decoder) processDHT(n int) error {
                }
 
                // Derive the look-up table.
-               for i := range h.lut {
-                       h.lut[i] = 0
-               }
+               clear(h.lut[:])
                var x, code uint32
                for i := uint32(0); i < lutSize; i++ {
                        code <<= 1

diff --git a/src/image/png/writer.go b/src/image/png/writer.go
index 9f92ad3d711597bf8580439c9c921173305c927d..101d908889b6b6fb5ee238be1dc2fddc0349d554 100644 (file)
--- a/src/image/png/writer.go
+++ b/src/image/png/writer.go
@@ -295,12 +295,6 @@ func filter(cr *[nFilter][]byte, pr []byte, bpp int) int {
        return filter
 }
 
-func zeroMemory(v []uint8) {
-       for i := range v {
-               v[i] = 0
-       }
-}
-
 func (e *encoder) writeImage(w io.Writer, m image.Image, cb int, level int) error {
        if e.zw == nil || e.zwLevel != level {
                zw, err := zlib.NewWriterLevel(w, level)
@@ -359,7 +353,7 @@ func (e *encoder) writeImage(w io.Writer, m image.Image, cb int, level int) erro
                e.pr = make([]uint8, sz)
        } else {
                e.pr = e.pr[:sz]
-               zeroMemory(e.pr)
+               clear(e.pr)
        }
        pr := e.pr