59 lines
2.3 KiB
Swift
59 lines
2.3 KiB
Swift
import Foundation
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import Testing
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@testable import Photochk
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@Suite("dHash")
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struct DHashTests {
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@Test("同じ値のハミング距離は 0")
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func identical() {
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#expect(DHash.hammingDistance(0xDEAD_BEEF_1234_5678, 0xDEAD_BEEF_1234_5678) == 0)
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}
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@Test("違うビットの数がそのまま距離になる")
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func differingBits() {
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#expect(DHash.hammingDistance(0, 0b1011) == 3)
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#expect(DHash.hammingDistance(.max, 0) == 64)
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#expect(DHash.hammingDistance(0b1100, 0b0110) == 2)
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}
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@Test("生成した画像から 64bit のハッシュが取れる")
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func computesFromImage() throws {
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let directory = try TestImages.makeTemporaryDirectory()
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defer { try? FileManager.default.removeItem(at: directory) }
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let url = directory.appendingPathComponent("base.jpg")
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try TestImages.writeJPEG(TestImages.pattern(seed: 1), to: url, quality: 0.9)
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let basics = try #require(DHash.compute(for: url))
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#expect(basics.pixelWidth == TestImages.width)
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#expect(basics.pixelHeight == TestImages.height)
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// 同じファイルからは必ず同じ値が出る
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let again = try #require(DHash.compute(for: url))
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#expect(basics.dHash == again.dHash)
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}
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@Test("リサイズしてもハッシュはほとんど変わらず、別の絵柄とは大きく離れる")
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func robustToResize() throws {
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let directory = try TestImages.makeTemporaryDirectory()
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defer { try? FileManager.default.removeItem(at: directory) }
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let base = directory.appendingPathComponent("base.jpg")
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let small = directory.appendingPathComponent("small.jpg")
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let other = directory.appendingPathComponent("other.jpg")
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let pattern = TestImages.pattern(seed: 7)
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try TestImages.writeJPEG(pattern, to: base, quality: 0.9)
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try TestImages.writeJPEG(TestImages.scaled(pattern, factor: 0.5), to: small, quality: 0.8)
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try TestImages.writeJPEG(TestImages.pattern(seed: 99), to: other, quality: 0.9)
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let baseHash = try #require(DHash.compute(for: base)).dHash
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let smallHash = try #require(DHash.compute(for: small)).dHash
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let otherHash = try #require(DHash.compute(for: other)).dHash
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#expect(DHash.hammingDistance(baseHash, smallHash) <= 12)
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#expect(DHash.hammingDistance(baseHash, otherHash) > 12)
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}
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}
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