diff options
Diffstat (limited to 'libgo/go/image/jpeg/dct_test.go')
| -rw-r--r-- | libgo/go/image/jpeg/dct_test.go | 26 |
1 files changed, 17 insertions, 9 deletions
diff --git a/libgo/go/image/jpeg/dct_test.go b/libgo/go/image/jpeg/dct_test.go index 770e274bac0..7389f7e4fe8 100644 --- a/libgo/go/image/jpeg/dct_test.go +++ b/libgo/go/image/jpeg/dct_test.go @@ -42,7 +42,7 @@ func TestDCT(t *testing.T) { b := block{} n := r.Int() % 64 for j := 0; j < n; j++ { - b[r.Int()%len(b)] = r.Int() % 256 + b[r.Int()%len(b)] = r.Int31() % 256 } blocks = append(blocks, b) } @@ -112,6 +112,14 @@ func alpha(i int) float64 { return math.Sqrt2 } +var cosines [32]float64 // cosines[k] = cos(π/2 * k/8) + +func init() { + for k := range cosines { + cosines[k] = math.Cos(math.Pi * float64(k) / 16) + } +} + // slowFDCT performs the 8*8 2-dimensional forward discrete cosine transform: // // dst[u,v] = (1/8) * Σ_x Σ_y alpha(u) * alpha(v) * src[x,y] * @@ -129,16 +137,16 @@ func slowFDCT(b *block) { for y := 0; y < 8; y++ { for x := 0; x < 8; x++ { sum += alpha(u) * alpha(v) * float64(b[8*y+x]) * - math.Cos(math.Pi*float64((2*x+1)*u)/16) * - math.Cos(math.Pi*float64((2*y+1)*v)/16) + cosines[((2*x+1)*u)%32] * + cosines[((2*y+1)*v)%32] } } dst[8*v+u] = sum / 8 } } - // Convert from float64 to int. + // Convert from float64 to int32. for i := range dst { - b[i] = int(dst[i] + 0.5) + b[i] = int32(dst[i] + 0.5) } } @@ -159,16 +167,16 @@ func slowIDCT(b *block) { for v := 0; v < 8; v++ { for u := 0; u < 8; u++ { sum += alpha(u) * alpha(v) * float64(b[8*v+u]) * - math.Cos(math.Pi*float64((2*x+1)*u)/16) * - math.Cos(math.Pi*float64((2*y+1)*v)/16) + cosines[((2*x+1)*u)%32] * + cosines[((2*y+1)*v)%32] } } dst[8*y+x] = sum / 8 } } - // Convert from float64 to int. + // Convert from float64 to int32. for i := range dst { - b[i] = int(dst[i] + 0.5) + b[i] = int32(dst[i] + 0.5) } } |