[performance] add benchmarks for native Go imaging code, small tweaks to reduce nil and boundary checks, some loop unrolling (#4482)

Reviewed-on: https://codeberg.org/superseriousbusiness/gotosocial/pulls/4482
Co-authored-by: kim <grufwub@gmail.com>
Co-committed-by: kim <grufwub@gmail.com>

internal/media/imaging_test.go

@@ -0,0 +1,157 @@
+// GoToSocial
+// Copyright (C) GoToSocial Authors admin@gotosocial.org
+// SPDX-License-Identifier: AGPL-3.0-or-later
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package media
+
+import (
+	"fmt"
+	"image"
+	"image/gif"
+	"image/jpeg"
+	"image/png"
+	"io"
+	"path"
+	"reflect"
+	"strings"
+	"testing"
+
+	"golang.org/x/image/webp"
+)
+
+func BenchmarkFlipH(b *testing.B) {
+	benchmarkFunc(b, func(img image.Image) {
+		_ = flipH(img)
+	})
+}
+
+func BenchmarkFlipV(b *testing.B) {
+	benchmarkFunc(b, func(img image.Image) {
+		_ = flipV(img)
+	})
+}
+
+func BenchmarkRotate90(b *testing.B) {
+	benchmarkFunc(b, func(img image.Image) {
+		_ = rotate90(img)
+	})
+}
+
+func BenchmarkRotate180(b *testing.B) {
+	benchmarkFunc(b, func(img image.Image) {
+		_ = rotate180(img)
+	})
+}
+
+func BenchmarkRotate270(b *testing.B) {
+	benchmarkFunc(b, func(img image.Image) {
+		_ = rotate270(img)
+	})
+}
+
+func BenchmarkTranspose(b *testing.B) {
+	benchmarkFunc(b, func(img image.Image) {
+		_ = transpose(img)
+	})
+}
+
+func BenchmarkTransverse(b *testing.B) {
+	benchmarkFunc(b, func(img image.Image) {
+		_ = transverse(img)
+	})
+}
+
+func BenchmarkResizeHorizontalLinear(b *testing.B) {
+	benchmarkFunc(b, func(img image.Image) {
+		_ = resizeHorizontalLinear(img, 64)
+	})
+}
+
+func BenchmarkResizeVerticalLinear(b *testing.B) {
+	benchmarkFunc(b, func(img image.Image) {
+		_ = resizeVerticalLinear(img, 64)
+	})
+}
+
+func benchmarkFunc(b *testing.B, fn func(image.Image)) {
+	b.Helper()
+	for _, testcase := range []struct {
+		Path   string
+		Decode func(io.Reader) (image.Image, error)
+	}{
+		{
+			Path:   "./test/big-panda.gif",
+			Decode: gif.Decode,
+		},
+		{
+			Path:   "./test/clock-original.gif",
+			Decode: gif.Decode,
+		},
+		{
+			Path:   "./test/test-jpeg.jpg",
+			Decode: jpeg.Decode,
+		},
+		{
+			Path:   "./test/test-png-noalphachannel.png",
+			Decode: png.Decode,
+		},
+		{
+			Path:   "./test/test-png-alphachannel.png",
+			Decode: png.Decode,
+		},
+		{
+			Path:   "./test/rainbow-original.png",
+			Decode: png.Decode,
+		},
+		{
+			Path:   "./test/nb-flag-original.webp",
+			Decode: webp.Decode,
+		},
+	} {
+		file, err := openRead(testcase.Path)
+		if err != nil {
+			panic(err)
+		}
+
+		img, err := testcase.Decode(file)
+		if err != nil {
+			panic(err)
+		}
+
+		info, err := file.Stat()
+		if err != nil {
+			panic(err)
+		}
+
+		file.Close()
+
+		testname := fmt.Sprintf("ext=%s type=%s size=%d",
+			strings.TrimPrefix(path.Ext(testcase.Path), "."),
+			strings.TrimPrefix(reflect.TypeOf(img).String(), "*image."),
+			info.Size(),
+		)
+
+		b.Run(testname, func(b *testing.B) {
+			b.Helper()
+			b.ResetTimer()
+			b.RunParallel(func(pb *testing.PB) {
+				for pb.Next() {
+					fn(img)
+				}
+			})
+		})
+	}
+}