heifer 0.3.12

Pure-Rust HEIF/HEIC image decoder and encoder: no C dependencies, no unsafe code
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270

//! Round trips through the encoder and the decoder.

use heifer::{EncodeOptions, Image, decode, encode, encode_rgb8, encode_rgba8};

/// A synthetic photo-like RGBA image: smooth gradients, edges and some texture, with an alpha
/// gradient in the bottom half when `alpha` is set.
fn test_image(w: u32, h: u32, alpha: bool) -> Vec<u8> {
    let mut out = Vec::with_capacity((w * h * 4) as usize);
    for y in 0..h {
        for x in 0..w {
            // Features a few pixels wide or more, as in photos.
            let (fx, fy) = (f64::from(x) / f64::from(w), f64::from(y) / f64::from(h));
            let (px, py) = (f64::from(x), f64::from(y));
            let ring =
                ((px - f64::from(w) / 2.0).hypot(py - f64::from(h) / 2.0) / 9.0).sin() * 30.0;
            let r = 60.0 + 150.0 * fx + ring;
            let g = 200.0 - 120.0 * fy
                + if (x / 37 + y / 23) % 2 == 0 {
                    25.0
                } else {
                    0.0
                };
            let b = 128.0 + 100.0 * (px / 31.0).sin() * (py / 23.0).cos();
            let a = if alpha && y >= h / 2 {
                255.0 * f64::from(x) / f64::from(w)
            } else {
                255.0
            };
            out.extend([r, g, b, a].map(|v| v.round().clamp(0.0, 255.0) as u8));
        }
    }
    out
}

fn psnr(a: &[u8], b: &[u8], channels: impl Fn(usize) -> bool) -> f64 {
    let (mut sum, mut n) = (0.0, 0usize);
    for (i, (&a, &b)) in a.iter().zip(b).enumerate() {
        if channels(i % 4) {
            sum += (f64::from(a) - f64::from(b)).powi(2);
            n += 1;
        }
    }
    10.0 * (255.0f64.powi(2) / (sum / n as f64).max(1e-9)).log10()
}

fn round_trip(w: u32, h: u32, alpha: bool, quality: u8) -> (Vec<u8>, Image, f64) {
    let rgba = test_image(w, h, alpha);
    let options = EncodeOptions {
        quality,
        ..EncodeOptions::default()
    };
    let heic = encode_rgba8(w, h, &rgba, &options).unwrap();
    let image = decode(&heic).unwrap();
    assert_eq!((image.width, image.height, image.bit_depth), (w, h, 8));
    assert_eq!(image.has_alpha, alpha);
    let decoded = image.to_rgba8();
    let p = psnr(&rgba, &decoded, |c| c < 3);
    if alpha {
        let pa = psnr(&rgba, &decoded, |c| c == 3);
        assert!(pa > 38.0, "{w}×{h} alpha: {pa:.1} dB");
    }
    (heic, image, p)
}

#[test]
fn small_images() {
    for (w, h) in [(16, 9), (64, 48), (77, 51), (512, 512)] {
        let (_, _, p) = round_trip(w, h, false, 80);
        assert!(p > 35.0, "{w}×{h}: {p:.1} dB");
    }
}

#[test]
fn tiny_images() {
    // A few pixels cannot keep their colours through 4:2:0 subsampling, but grey levels stay.
    for (w, h) in [(1, 1), (2, 3), (3, 2), (5, 7)] {
        let rgba: Vec<u8> = (0..w * h)
            .flat_map(|i| {
                let v = (i * 37 % 200) as u8;
                [v, v, v, 255]
            })
            .collect();
        let options = EncodeOptions {
            quality: 100,
            ..EncodeOptions::default()
        };
        let image = decode(&encode_rgba8(w, h, &rgba, &options).unwrap()).unwrap();
        assert_eq!((image.width, image.height), (w, h));
        let error = rgba
            .iter()
            .zip(image.to_rgba8())
            .map(|(&a, b)| a.abs_diff(b))
            .max();
        assert!(error <= Some(2), "{w}×{h}: {error:?}");
    }
}

#[test]
fn grid_images() {
    // 3×2 tiles, the last column and row partly outside the image.
    let (heic, _, p) = round_trip(1100, 700, false, 80);
    assert!(p > 35.0, "{p:.1} dB");
    let file = heifer::heifer_isobmff::HeifFile::parse(&heic).unwrap();
    let grid = file.grid(file.primary_id).unwrap();
    assert_eq!((grid.rows, grid.columns), (2, 3));
}

#[test]
fn alpha() {
    for (w, h) in [(33, 17), (600, 300)] {
        let (_, image, p) = round_trip(w, h, true, 80);
        assert!(p > 35.0, "{w}×{h}: {p:.1} dB");
        // Opaque top half, transparent left of the bottom half.
        assert_eq!(image.data[3], 255);
        let bottom_left = ((h - 1) * w) as usize * 4 + 3;
        assert!(image.data[bottom_left] < 8);
    }
}

#[test]
fn quality_controls_size_and_fidelity() {
    let results: Vec<(usize, f64)> = [20, 50, 80, 95]
        .iter()
        .map(|&q| {
            let (heic, _, p) = round_trip(256, 192, false, q);
            (heic.len(), p)
        })
        .collect();
    for pair in results.windows(2) {
        assert!(
            pair[0].0 < pair[1].0 && pair[0].1 < pair[1].1,
            "{results:?}"
        );
    }
}

#[test]
fn encode_decoded_image_and_rgb() {
    let rgba = test_image(40, 30, false);
    let rgb: Vec<u8> = rgba
        .chunks_exact(4)
        .flat_map(|p| [p[0], p[1], p[2]])
        .collect();
    let options = EncodeOptions::default();
    let from_rgb = encode_rgb8(40, 30, &rgb, &options).unwrap();
    let from_rgba = encode_rgba8(40, 30, &rgba, &options).unwrap();
    assert_eq!(from_rgb, from_rgba);
    let image = decode(&from_rgb).unwrap();
    let again = encode(&image, &options).unwrap();
    assert!(!decode(&again).unwrap().has_alpha);
}

#[test]
fn rejects_bad_input() {
    let options = EncodeOptions::default();
    assert!(encode_rgba8(0, 1, &[], &options).is_err());
    assert!(encode_rgba8(2, 2, &[0; 15], &options).is_err());
    assert!(encode_rgb8(2, 2, &[0; 16], &options).is_err());
}

#[test]
fn metadata_is_kept() {
    let rgba = test_image(600, 300, false); // a grid: metadata goes on the grid item
    let image = decode(&encode_rgba8(600, 300, &rgba, &EncodeOptions::default()).unwrap()).unwrap();
    let metadata = heifer::Metadata {
        exif: Some(b"II*\0\x08\0\0\0\0\0".to_vec()),
        xmp: Some(b"<x:xmpmeta/>".to_vec()),
        icc_profile: Some(b"icc".to_vec()),
    };
    let heic = heifer::encode_with_metadata(&image, &metadata, &EncodeOptions::default()).unwrap();
    assert_eq!(heifer::read_metadata(&heic).unwrap(), metadata);
    assert_eq!(decode(&heic).unwrap().width, 600);
}

#[test]
fn deep_images_are_coded_in_10_bits() {
    // A smooth 16-bit gradient: 8 bits would leave at most 256 grey levels (visible steps).
    let (w, h) = (1024u32, 64u32);
    let mut data = Vec::new();
    for y in 0..h {
        for x in 0..w {
            let v = (x * 64) as u16;
            let a = if y < 32 { 65535 } else { (x * 64) as u16 };
            data.extend([v, v, v, a]);
        }
    }
    let image = Image {
        width: w,
        height: h,
        bit_depth: 16,
        has_alpha: true,
        data,
    };
    let options = EncodeOptions {
        quality: 90,
        ..EncodeOptions::default()
    };
    let heic = encode(&image, &options).unwrap();
    let file = heifer::heifer_isobmff::HeifFile::parse(&heic).unwrap();
    let tiles = file.referenced_items(file.primary_id, b"dimg");
    let config = file.hevc_config(tiles[0]).unwrap().unwrap();
    assert_eq!(
        (config.profile_idc, config.bit_depth_luma),
        (2, 10),
        "Main 10"
    );

    let decoded = decode(&heic).unwrap();
    assert_eq!(
        (decoded.width, decoded.height, decoded.bit_depth),
        (w, h, 10)
    );
    assert!(decoded.has_alpha);
    let row: Vec<u16> = (0..w as usize)
        .map(|x| decoded.data[(10 * w as usize + x) * 4])
        .collect();
    let mut levels = row.clone();
    levels.sort_unstable();
    levels.dedup();
    assert!(levels.len() > 600, "{} grey levels", levels.len());
    // Close to the original (scaled to 10 bits).
    let max_error = row
        .iter()
        .enumerate()
        .map(|(x, &v)| (i32::from(v) - (x as i32 * 64 * 1023 / 65535)).abs())
        .max();
    assert!(max_error <= Some(6), "{max_error:?}");
}

#[test]
fn large_images_get_a_thumbnail() {
    let (w, h) = (1100, 700);
    let rgba = test_image(w, h, true);
    let heic = encode_rgba8(w, h, &rgba, &EncodeOptions::default()).unwrap();
    let thumb = heifer::decode_thumbnail(&heic)
        .unwrap()
        .expect("a thumbnail");
    // Longest side 320, same aspect ratio, alpha kept.
    assert_eq!((thumb.width, thumb.height), (320, 204));
    assert!(thumb.has_alpha);
    // It looks like the image: compare with a box-filtered copy of the pixels.
    let thumb8 = thumb.to_rgba8();
    let mut sum_error = 0.0;
    for (i, px) in thumb8.chunks_exact(4).enumerate() {
        let (tx, ty) = (i % 320, i / 320);
        let (x, y) = (tx * w as usize / 320 + 1, ty * h as usize / 204 + 1);
        let src = &rgba[(y * w as usize + x) * 4..][..3];
        sum_error += px
            .iter()
            .zip(src)
            .map(|(&a, &b)| f64::from(a.abs_diff(b)))
            .sum::<f64>();
    }
    let mean = sum_error / (320.0 * 204.0 * 3.0);
    assert!(mean < 12.0, "mean error {mean:.1}");
    // The primary image is unchanged by the thumbnail.
    assert_eq!(decode(&heic).unwrap().width, w);
}

#[test]
fn small_images_have_no_thumbnail() {
    let heic = encode_rgba8(
        64,
        48,
        &test_image(64, 48, false),
        &EncodeOptions::default(),
    )
    .unwrap();
    assert!(heifer::decode_thumbnail(&heic).unwrap().is_none());
}