| // Copyright 2026 The Wuffs Authors. |
| // |
| // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or |
| // https://www.apache.org/licenses/LICENSE-2.0> or the MIT license |
| // <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your |
| // option. This file may not be copied, modified, or distributed |
| // except according to those terms. |
| // |
| // SPDX-License-Identifier: Apache-2.0 OR MIT |
| |
| package lowleveldct4x4 |
| |
| import ( |
| "testing" |
| ) |
| |
| func diffU8(a uint8, b uint8) uint8 { |
| if a < b { |
| return b - a |
| } |
| return a - b |
| } |
| |
| func TestRoundTrip(tt *testing.T) { |
| // src is an excerpt of pjw8x8 in lowleveljpeg's unit tests. |
| src := BlockU8{ |
| 0xFF, 0xFF, 0xAF, 0x40, |
| 0xFF, 0xEF, 0xEF, 0xFF, |
| 0xFF, 0x60, 0xDF, 0xFF, |
| 0xA0, 0x00, 0x90, 0x70, |
| } |
| |
| got := src.ForwardDCT() |
| want := BlockI16{ |
| +0x00EA, +0x0034, +0x003C, +0x005F, |
| +0x0082, +0x006E, -0x0064, -0x005D, |
| -0x00A3, +0x0057, -0x0034, +0x000C, |
| -0x0007, +0x0013, +0x0014, +0x0019, |
| } |
| if got != want { |
| tt.Fatalf("incorrect DCT\n\n%v\n%v", got, want) |
| } |
| |
| dst := got.InverseDCT() |
| const toleranceU8 = 1 |
| for i := range src { |
| if diffU8(src[i], dst[i]) > toleranceU8 { |
| tt.Fatalf("difference was too big at (%d, %d)\n\n%v\n%v", |
| i&3, i>>2, src, dst) |
| } |
| } |
| } |
