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
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
//! Image Processing Functions
use std::cmp;

use crate::image::{GenericImage, GenericImageView, SubImage};
use crate::traits::{Lerp, Pixel, Primitive};

pub use self::sample::FilterType;

pub use self::sample::FilterType::{CatmullRom, Gaussian, Lanczos3, Nearest, Triangle};

/// Affine transformations
pub use self::affine::{
    flip_horizontal, flip_horizontal_in, flip_horizontal_in_place, flip_vertical, flip_vertical_in,
    flip_vertical_in_place, rotate180, rotate180_in, rotate180_in_place, rotate270, rotate270_in,
    rotate90, rotate90_in,
};

/// Image sampling
pub use self::sample::{blur, filter3x3, resize, thumbnail, unsharpen};

/// Color operations
pub use self::colorops::{
    brighten, contrast, dither, grayscale, grayscale_alpha, grayscale_with_type,
    grayscale_with_type_alpha, huerotate, index_colors, invert, BiLevel, ColorMap,
};

mod affine;
// Public only because of Rust bug:
// https://github.com/rust-lang/rust/issues/18241
pub mod colorops;
mod sample;

/// Return a mutable view into an image
/// The coordinates set the position of the top left corner of the crop.
pub fn crop<I: GenericImageView>(
    image: &mut I,
    x: u32,
    y: u32,
    width: u32,
    height: u32,
) -> SubImage<&mut I> {
    let (x, y, width, height) = crop_dimms(image, x, y, width, height);
    SubImage::new(image, x, y, width, height)
}

/// Return an immutable view into an image
/// The coordinates set the position of the top left corner of the crop.
pub fn crop_imm<I: GenericImageView>(
    image: &I,
    x: u32,
    y: u32,
    width: u32,
    height: u32,
) -> SubImage<&I> {
    let (x, y, width, height) = crop_dimms(image, x, y, width, height);
    SubImage::new(image, x, y, width, height)
}

fn crop_dimms<I: GenericImageView>(
    image: &I,
    x: u32,
    y: u32,
    width: u32,
    height: u32,
) -> (u32, u32, u32, u32) {
    let (iwidth, iheight) = image.dimensions();

    let x = cmp::min(x, iwidth);
    let y = cmp::min(y, iheight);

    let height = cmp::min(height, iheight - y);
    let width = cmp::min(width, iwidth - x);

    (x, y, width, height)
}

/// Calculate the region that can be copied from top to bottom.
///
/// Given image size of bottom and top image, and a point at which we want to place the top image
/// onto the bottom image, how large can we be? Have to wary of the following issues:
/// * Top might be larger than bottom
/// * Overflows in the computation
/// * Coordinates could be completely out of bounds
///
/// The main idea is to make use of inequalities provided by the nature of `saturating_add` and
/// `saturating_sub`. These intrinsically validate that all resulting coordinates will be in bounds
/// for both images.
///
/// We want that all these coordinate accesses are safe:
/// 1. `bottom.get_pixel(x + [0..x_range), y + [0..y_range))`
/// 2. `top.get_pixel([0..x_range), [0..y_range))`
///
/// Proof that the function provides the necessary bounds for width. Note that all unaugmented math
/// operations are to be read in standard arithmetic, not integer arithmetic. Since no direct
/// integer arithmetic occurs in the implementation, this is unambiguous.
///
/// ```text
/// Three short notes/lemmata:
/// - Iff `(a - b) <= 0` then `a.saturating_sub(b) = 0`
/// - Iff `(a - b) >= 0` then `a.saturating_sub(b) = a - b`
/// - If  `a <= c` then `a.saturating_sub(b) <= c.saturating_sub(b)`
///
/// 1.1 We show that if `bottom_width <= x`, then `x_range = 0` therefore `x + [0..x_range)` is empty.
///
/// x_range
///  = (top_width.saturating_add(x).min(bottom_width)).saturating_sub(x)
/// <= bottom_width.saturating_sub(x)
///
/// bottom_width <= x
/// <==> bottom_width - x <= 0
/// <==> bottom_width.saturating_sub(x) = 0
///  ==> x_range <= 0
///  ==> x_range  = 0
///
/// 1.2 If `x < bottom_width` then `x + x_range < bottom_width`
///
/// x + x_range
/// <= x + bottom_width.saturating_sub(x)
///  = x + (bottom_width - x)
///  = bottom_width
///
/// 2. We show that `x_range <= top_width`
///
/// x_range
///  = (top_width.saturating_add(x).min(bottom_width)).saturating_sub(x)
/// <= top_width.saturating_add(x).saturating_sub(x)
/// <= (top_wdith + x).saturating_sub(x)
///  = top_width (due to `top_width >= 0` and `x >= 0`)
/// ```
///
/// Proof is the same for height.
pub fn overlay_bounds(
    (bottom_width, bottom_height): (u32, u32),
    (top_width, top_height): (u32, u32),
    x: u32,
    y: u32,
) -> (u32, u32) {
    let x_range = top_width
        .saturating_add(x) // Calculate max coordinate
        .min(bottom_width) // Restrict to lower width
        .saturating_sub(x); // Determinate length from start `x`
    let y_range = top_height
        .saturating_add(y)
        .min(bottom_height)
        .saturating_sub(y);
    (x_range, y_range)
}

/// Calculate the region that can be copied from top to bottom.
///
/// Given image size of bottom and top image, and a point at which we want to place the top image
/// onto the bottom image, how large can we be? Have to wary of the following issues:
/// * Top might be larger than bottom
/// * Overflows in the computation
/// * Coordinates could be completely out of bounds
///
/// The returned value is of the form:
///
/// `(origin_bottom_x, origin_bottom_y, origin_top_x, origin_top_y, x_range, y_range)`
///
/// The main idea is to do computations on i64's and then clamp to image dimensions.
/// In particular, we want to ensure that all these coordinate accesses are safe:
/// 1. `bottom.get_pixel(origin_bottom_x + [0..x_range), origin_bottom_y + [0..y_range))`
/// 2. `top.get_pixel(origin_top_y + [0..x_range), origin_top_y + [0..y_range))`
///
fn overlay_bounds_ext(
    (bottom_width, bottom_height): (u32, u32),
    (top_width, top_height): (u32, u32),
    x: i64,
    y: i64,
) -> (u32, u32, u32, u32, u32, u32) {
    // Return a predictable value if the two images don't overlap at all.
    if x > i64::from(bottom_width)
        || y > i64::from(bottom_height)
        || x.saturating_add(i64::from(top_width)) <= 0
        || y.saturating_add(i64::from(top_height)) <= 0
    {
        return (0, 0, 0, 0, 0, 0);
    }

    // Find the maximum x and y coordinates in terms of the bottom image.
    let max_x = x.saturating_add(i64::from(top_width));
    let max_y = y.saturating_add(i64::from(top_height));

    // Clip the origin and maximum coordinates to the bounds of the bottom image.
    // Casting to a u32 is safe because both 0 and `bottom_{width,height}` fit
    // into 32-bits.
    let max_inbounds_x = max_x.clamp(0, i64::from(bottom_width)) as u32;
    let max_inbounds_y = max_y.clamp(0, i64::from(bottom_height)) as u32;
    let origin_bottom_x = x.clamp(0, i64::from(bottom_width)) as u32;
    let origin_bottom_y = y.clamp(0, i64::from(bottom_height)) as u32;

    // The range is the difference between the maximum inbounds coordinates and
    // the clipped origin. Unchecked subtraction is safe here because both are
    // always positive and `max_inbounds_{x,y}` >= `origin_{x,y}` due to
    // `top_{width,height}` being >= 0.
    let x_range = max_inbounds_x - origin_bottom_x;
    let y_range = max_inbounds_y - origin_bottom_y;

    // If x (or y) is negative, then the origin of the top image is shifted by -x (or -y).
    let origin_top_x = x.saturating_mul(-1).clamp(0, i64::from(top_width)) as u32;
    let origin_top_y = y.saturating_mul(-1).clamp(0, i64::from(top_height)) as u32;

    (
        origin_bottom_x,
        origin_bottom_y,
        origin_top_x,
        origin_top_y,
        x_range,
        y_range,
    )
}

/// Overlay an image at a given coordinate (x, y)
pub fn overlay<I, J>(bottom: &mut I, top: &J, x: i64, y: i64)
where
    I: GenericImage,
    J: GenericImageView<Pixel = I::Pixel>,
{
    let bottom_dims = bottom.dimensions();
    let top_dims = top.dimensions();

    // Crop our top image if we're going out of bounds
    let (origin_bottom_x, origin_bottom_y, origin_top_x, origin_top_y, range_width, range_height) =
        overlay_bounds_ext(bottom_dims, top_dims, x, y);

    for y in 0..range_height {
        for x in 0..range_width {
            let p = top.get_pixel(origin_top_x + x, origin_top_y + y);
            let mut bottom_pixel = bottom.get_pixel(origin_bottom_x + x, origin_bottom_y + y);
            bottom_pixel.blend(&p);

            bottom.put_pixel(origin_bottom_x + x, origin_bottom_y + y, bottom_pixel);
        }
    }
}

/// Tile an image by repeating it multiple times
///
/// # Examples
/// ```no_run
/// use image::{RgbaImage};
///
/// let mut img = RgbaImage::new(1920, 1080);
/// let tile = image::open("tile.png").unwrap();
///
/// image::imageops::tile(&mut img, &tile);
/// img.save("tiled_wallpaper.png").unwrap();
/// ```
pub fn tile<I, J>(bottom: &mut I, top: &J)
where
    I: GenericImage,
    J: GenericImageView<Pixel = I::Pixel>,
{
    for x in (0..bottom.width()).step_by(top.width() as usize) {
        for y in (0..bottom.height()).step_by(top.height() as usize) {
            overlay(bottom, top, i64::from(x), i64::from(y));
        }
    }
}

/// Fill the image with a linear vertical gradient
///
/// This function assumes a linear color space.
///
/// # Examples
/// ```no_run
/// use image::{Rgba, RgbaImage, Pixel};
///
/// let mut img = RgbaImage::new(100, 100);
/// let start = Rgba::from_slice(&[0, 128, 0, 0]);
/// let end = Rgba::from_slice(&[255, 255, 255, 255]);
///
/// image::imageops::vertical_gradient(&mut img, start, end);
/// img.save("vertical_gradient.png").unwrap();
pub fn vertical_gradient<S, P, I>(img: &mut I, start: &P, stop: &P)
where
    I: GenericImage<Pixel = P>,
    P: Pixel<Subpixel = S> + 'static,
    S: Primitive + Lerp + 'static,
{
    for y in 0..img.height() {
        let pixel = start.map2(stop, |a, b| {
            let y = <S::Ratio as num_traits::NumCast>::from(y).unwrap();
            let height = <S::Ratio as num_traits::NumCast>::from(img.height() - 1).unwrap();
            S::lerp(a, b, y / height)
        });

        for x in 0..img.width() {
            img.put_pixel(x, y, pixel);
        }
    }
}

/// Fill the image with a linear horizontal gradient
///
/// This function assumes a linear color space.
///
/// # Examples
/// ```no_run
/// use image::{Rgba, RgbaImage, Pixel};
///
/// let mut img = RgbaImage::new(100, 100);
/// let start = Rgba::from_slice(&[0, 128, 0, 0]);
/// let end = Rgba::from_slice(&[255, 255, 255, 255]);
///
/// image::imageops::horizontal_gradient(&mut img, start, end);
/// img.save("horizontal_gradient.png").unwrap();
pub fn horizontal_gradient<S, P, I>(img: &mut I, start: &P, stop: &P)
where
    I: GenericImage<Pixel = P>,
    P: Pixel<Subpixel = S> + 'static,
    S: Primitive + Lerp + 'static,
{
    for x in 0..img.width() {
        let pixel = start.map2(stop, |a, b| {
            let x = <S::Ratio as num_traits::NumCast>::from(x).unwrap();
            let width = <S::Ratio as num_traits::NumCast>::from(img.width() - 1).unwrap();
            S::lerp(a, b, x / width)
        });

        for y in 0..img.height() {
            img.put_pixel(x, y, pixel);
        }
    }
}

/// Replace the contents of an image at a given coordinate (x, y)
pub fn replace<I, J>(bottom: &mut I, top: &J, x: i64, y: i64)
where
    I: GenericImage,
    J: GenericImageView<Pixel = I::Pixel>,
{
    let bottom_dims = bottom.dimensions();
    let top_dims = top.dimensions();

    // Crop our top image if we're going out of bounds
    let (origin_bottom_x, origin_bottom_y, origin_top_x, origin_top_y, range_width, range_height) =
        overlay_bounds_ext(bottom_dims, top_dims, x, y);

    for y in 0..range_height {
        for x in 0..range_width {
            let p = top.get_pixel(origin_top_x + x, origin_top_y + y);
            bottom.put_pixel(origin_bottom_x + x, origin_bottom_y + y, p);
        }
    }
}

#[cfg(test)]
mod tests {

    use super::{overlay, overlay_bounds_ext};
    use crate::color::Rgb;
    use crate::ImageBuffer;
    use crate::RgbaImage;

    #[test]
    fn test_overlay_bounds_ext() {
        assert_eq!(
            overlay_bounds_ext((10, 10), (10, 10), 0, 0),
            (0, 0, 0, 0, 10, 10)
        );
        assert_eq!(
            overlay_bounds_ext((10, 10), (10, 10), 1, 0),
            (1, 0, 0, 0, 9, 10)
        );
        assert_eq!(
            overlay_bounds_ext((10, 10), (10, 10), 0, 11),
            (0, 0, 0, 0, 0, 0)
        );
        assert_eq!(
            overlay_bounds_ext((10, 10), (10, 10), -1, 0),
            (0, 0, 1, 0, 9, 10)
        );
        assert_eq!(
            overlay_bounds_ext((10, 10), (10, 10), -10, 0),
            (0, 0, 0, 0, 0, 0)
        );
        assert_eq!(
            overlay_bounds_ext((10, 10), (10, 10), 1i64 << 50, 0),
            (0, 0, 0, 0, 0, 0)
        );
        assert_eq!(
            overlay_bounds_ext((10, 10), (10, 10), -(1i64 << 50), 0),
            (0, 0, 0, 0, 0, 0)
        );
        assert_eq!(
            overlay_bounds_ext((10, 10), (u32::MAX, 10), 10 - i64::from(u32::MAX), 0),
            (0, 0, u32::MAX - 10, 0, 10, 10)
        );
    }

    #[test]
    /// Test that images written into other images works
    fn test_image_in_image() {
        let mut target = ImageBuffer::new(32, 32);
        let source = ImageBuffer::from_pixel(16, 16, Rgb([255u8, 0, 0]));
        overlay(&mut target, &source, 0, 0);
        assert!(*target.get_pixel(0, 0) == Rgb([255u8, 0, 0]));
        assert!(*target.get_pixel(15, 0) == Rgb([255u8, 0, 0]));
        assert!(*target.get_pixel(16, 0) == Rgb([0u8, 0, 0]));
        assert!(*target.get_pixel(0, 15) == Rgb([255u8, 0, 0]));
        assert!(*target.get_pixel(0, 16) == Rgb([0u8, 0, 0]));
    }

    #[test]
    /// Test that images written outside of a frame doesn't blow up
    fn test_image_in_image_outside_of_bounds() {
        let mut target = ImageBuffer::new(32, 32);
        let source = ImageBuffer::from_pixel(32, 32, Rgb([255u8, 0, 0]));
        overlay(&mut target, &source, 1, 1);
        assert!(*target.get_pixel(0, 0) == Rgb([0, 0, 0]));
        assert!(*target.get_pixel(1, 1) == Rgb([255u8, 0, 0]));
        assert!(*target.get_pixel(31, 31) == Rgb([255u8, 0, 0]));
    }

    #[test]
    /// Test that images written to coordinates out of the frame doesn't blow up
    /// (issue came up in #848)
    fn test_image_outside_image_no_wrap_around() {
        let mut target = ImageBuffer::new(32, 32);
        let source = ImageBuffer::from_pixel(32, 32, Rgb([255u8, 0, 0]));
        overlay(&mut target, &source, 33, 33);
        assert!(*target.get_pixel(0, 0) == Rgb([0, 0, 0]));
        assert!(*target.get_pixel(1, 1) == Rgb([0, 0, 0]));
        assert!(*target.get_pixel(31, 31) == Rgb([0, 0, 0]));
    }

    #[test]
    /// Test that images written to coordinates with overflow works
    fn test_image_coordinate_overflow() {
        let mut target = ImageBuffer::new(16, 16);
        let source = ImageBuffer::from_pixel(32, 32, Rgb([255u8, 0, 0]));
        // Overflows to 'sane' coordinates but top is larger than bot.
        overlay(
            &mut target,
            &source,
            i64::from(u32::max_value() - 31),
            i64::from(u32::max_value() - 31),
        );
        assert!(*target.get_pixel(0, 0) == Rgb([0, 0, 0]));
        assert!(*target.get_pixel(1, 1) == Rgb([0, 0, 0]));
        assert!(*target.get_pixel(15, 15) == Rgb([0, 0, 0]));
    }

    use super::{horizontal_gradient, vertical_gradient};

    #[test]
    /// Test that horizontal gradients are correctly generated
    fn test_image_horizontal_gradient_limits() {
        let mut img = ImageBuffer::new(100, 1);

        let start = Rgb([0u8, 128, 0]);
        let end = Rgb([255u8, 255, 255]);

        horizontal_gradient(&mut img, &start, &end);

        assert_eq!(img.get_pixel(0, 0), &start);
        assert_eq!(img.get_pixel(img.width() - 1, 0), &end);
    }

    #[test]
    /// Test that vertical gradients are correctly generated
    fn test_image_vertical_gradient_limits() {
        let mut img = ImageBuffer::new(1, 100);

        let start = Rgb([0u8, 128, 0]);
        let end = Rgb([255u8, 255, 255]);

        vertical_gradient(&mut img, &start, &end);

        assert_eq!(img.get_pixel(0, 0), &start);
        assert_eq!(img.get_pixel(0, img.height() - 1), &end);
    }

    #[test]
    /// Test blur doesn't panick when passed 0.0
    fn test_blur_zero() {
        let image = RgbaImage::new(50, 50);
        let _ = super::blur(&image, 0.0);
    }
}