heifer 0.3.17

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

//! Encoding of HDR images with an ISO 21496-1 gain map.

use heifer::heifer_isobmff::HeifFile;
use heifer::{EncodeOptions, HdrImage, Image, encode_hdr, encode_hdr_with_metadata};

fn load(name: &str) -> Option<Vec<u8>> {
    let path = format!("{}/../../tests/fixtures/{name}", env!("CARGO_MANIFEST_DIR"));
    let data = std::fs::read(&path).ok();
    if data.is_none() {
        eprintln!("skipping: {path} not found (run scripts/fetch-fixtures.sh)");
    }
    data
}

fn srgb_to_linear(v: f32) -> f32 {
    if v <= 0.04045 {
        v / 12.92
    } else {
        ((v + 0.055) / 1.055).powf(2.4)
    }
}

/// A grey gradient whose central square is four times brighter in the HDR rendition.
fn synthetic(w: u32, h: u32) -> (Image, HdrImage) {
    let mut base = Image::filled(w, h, 8, [0, 0, 0, 255]);
    let mut hdr = HdrImage {
        width: w,
        height: h,
        headroom: 4.0,
        data: vec![0.0; w as usize * h as usize * 3],
    };
    for y in 0..h {
        for x in 0..w {
            let i = (y * w + x) as usize;
            let v = (40 + 160 * x / (w - 1)) as u8;
            base.data[i * 4] = u16::from(v);
            base.data[i * 4 + 1] = u16::from(v);
            base.data[i * 4 + 2] = u16::from(v);
            let patch = (w / 4..w / 2).contains(&x) && (h / 4..h / 2).contains(&y);
            let gain = if patch { 4.0 } else { 1.0 };
            for c in 0..3 {
                hdr.data[i * 3 + c] = srgb_to_linear(f32::from(v) / 255.0) * gain;
            }
        }
    }
    (base, hdr)
}

#[test]
fn gain_map_round_trips() {
    let (base, hdr) = synthetic(64, 48);
    let options = EncodeOptions {
        quality: 90,
        ..EncodeOptions::default()
    };
    let bytes = encode_hdr(&base, &hdr, &options).unwrap();

    let file = HeifFile::parse(&bytes).unwrap();
    assert!(file.file_type.has_brand(b"tmap"));
    let tmap = file
        .items
        .iter()
        .find(|item| item.item_type.0 == *b"tmap")
        .unwrap();
    let references = file.referenced_items(tmap.id, b"dimg");
    let [base_id, map_id] = references else {
        panic!("expected two dimg references, got {references:?}");
    };
    assert_eq!(*base_id, file.primary_id);
    assert_eq!(file.image_size(*map_id).unwrap(), Some((32, 24)));
    assert!(file.item(*map_id).unwrap().hidden);
    assert!(!file.item(tmap.id).unwrap().hidden);
    assert_eq!(file.hevc_config(*map_id).unwrap().unwrap().chroma_format, 0);
    let payload = file.item_data(tmap.id).unwrap();
    assert_eq!(payload.len(), 62);
    assert_eq!(payload[5], 0x40); // use_base_colour_space, one channel
    assert!(bytes.windows(4).any(|w| w == b"altr"));

    let decoded =
        heifer::hdr::decode_hdr_with_options(&bytes, &Default::default(), f32::INFINITY).unwrap();
    assert_eq!((decoded.width, decoded.height), (64, 48));
    assert!((decoded.headroom - 4.0).abs() < 0.01);
    let base_back = heifer::decode(&bytes).unwrap();
    for y in 0..48 {
        for x in 0..64 {
            // The half-resolution gain map cannot represent the two-pixel ramp at a hard edge.
            let in_patch = (18..30).contains(&x) && (14..22).contains(&y);
            let flat = !((14..34).contains(&x) && (10..26).contains(&y));
            if !(in_patch || flat) {
                continue;
            }
            let i = (y * 64 + x) as usize;
            let gain = if in_patch { 4.0 } else { 1.0 };
            for c in 0..3 {
                let sample = f32::from(base_back.data[i * 4 + c]) / 255.0;
                let expected = srgb_to_linear(sample) * gain;
                let got = decoded.data[i * 3 + c];
                let error = (got - expected).abs();
                assert!(
                    error <= 0.02 * expected + 0.001,
                    "({x}, {y}) channel {c}: expected {expected}, got {got}"
                );
            }
        }
    }
}

#[test]
fn gain_map_of_a_grid_is_a_hidden_half_size_grid() {
    let (base, hdr) = synthetic(1100, 700);
    let options = EncodeOptions {
        quality: 60,
        ..EncodeOptions::default()
    };
    let bytes = encode_hdr(&base, &hdr, &options).unwrap();

    let file = HeifFile::parse(&bytes).unwrap();
    let tmap = file
        .items
        .iter()
        .find(|item| item.item_type.0 == *b"tmap")
        .unwrap();
    let references = file.referenced_items(tmap.id, b"dimg");
    let [base_id, map_id] = references else {
        panic!("expected two dimg references, got {references:?}");
    };
    assert_eq!(*base_id, file.primary_id);
    assert_eq!(file.image_size(tmap.id).unwrap(), Some((1100, 700)));
    assert_eq!(file.image_size(*map_id).unwrap(), Some((550, 350)));
    assert!(file.item(*map_id).unwrap().hidden);
    let grid = file.grid(*map_id).unwrap();
    assert_eq!((grid.rows, grid.columns), (1, 2));
    for &tile in file.referenced_items(*map_id, b"dimg") {
        assert_eq!(file.hevc_config(tile).unwrap().unwrap().chroma_format, 0);
    }

    let decoded =
        heifer::hdr::decode_hdr_with_options(&bytes, &Default::default(), f32::INFINITY).unwrap();
    assert_eq!((decoded.width, decoded.height), (1100, 700));
    assert!((decoded.headroom - 4.0).abs() < 0.01);
}

#[test]
fn hdr_metadata_is_kept() {
    let (base, hdr) = synthetic(64, 48);
    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 bytes =
        encode_hdr_with_metadata(&base, &hdr, &metadata, &EncodeOptions::default()).unwrap();
    assert_eq!(heifer::read_metadata(&bytes).unwrap(), metadata);
    assert!(
        heifer::hdr::decode_hdr_with_options(&bytes, &Default::default(), f32::INFINITY).is_ok()
    );
}

#[test]
fn rejects_bad_hdr_input() {
    let (base, hdr) = synthetic(64, 48);
    let options = EncodeOptions::default();

    let mut wrong_size = hdr.clone();
    wrong_size.width = 32;
    assert!(encode_hdr(&base, &wrong_size, &options).is_err());

    let mut truncated = hdr.clone();
    truncated.data.pop();
    assert!(encode_hdr(&base, &truncated, &options).is_err());

    for headroom in [1.0, 0.5, f32::NAN, f32::INFINITY] {
        let mut flat = hdr.clone();
        flat.headroom = headroom;
        assert!(encode_hdr(&base, &flat, &options).is_err(), "{headroom}");
    }
}

#[test]
fn reencodes_a_real_samsung_gain_map() {
    let Some(bytes) = load("real/heif_special__aux_YCbCr.heic") else {
        return;
    };
    let base = heifer::decode(&bytes).unwrap();
    let hdr =
        heifer::hdr::decode_hdr_with_options(&bytes, &Default::default(), f32::INFINITY).unwrap();

    // A 512×512 crop around the brightest highlights keeps the test fast.
    let (x0, y0, size) = (704usize, 192usize, 512usize);
    let base = base.crop(x0 as u32, y0 as u32, size as u32, size as u32);
    let mut data = Vec::with_capacity(size * size * 3);
    for y in 0..size {
        let start = ((y + y0) * hdr.width as usize + x0) * 3;
        data.extend_from_slice(&hdr.data[start..start + size * 3]);
    }
    let crop = HdrImage {
        width: size as u32,
        height: size as u32,
        headroom: hdr.headroom,
        data,
    };

    let options = EncodeOptions {
        quality: 90,
        ..EncodeOptions::default()
    };
    let out = encode_hdr(&base, &crop, &options).unwrap();
    let back =
        heifer::hdr::decode_hdr_with_options(&out, &Default::default(), f32::INFINITY).unwrap();
    assert!((back.headroom - crop.headroom).abs() < 0.01);
    assert_eq!((back.width, back.height), (size as u32, size as u32));

    let (mut sum, mut max) = (0.0f64, 0.0f32);
    for (&expected, &got) in crop.data.iter().zip(&back.data) {
        let error = (got - expected).abs();
        sum += f64::from(error);
        max = max.max(error);
    }
    let mean = sum / crop.data.len() as f64;
    assert!(mean < 0.01, "mean error {mean}");
    assert!(max < 0.15, "max error {max}");
}