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Diffstat (limited to 'vendor/image/src/codecs/jpeg/transform.rs')
| -rw-r--r-- | vendor/image/src/codecs/jpeg/transform.rs | 196 |
1 files changed, 196 insertions, 0 deletions
diff --git a/vendor/image/src/codecs/jpeg/transform.rs b/vendor/image/src/codecs/jpeg/transform.rs new file mode 100644 index 0000000..1ca01a9 --- /dev/null +++ b/vendor/image/src/codecs/jpeg/transform.rs @@ -0,0 +1,196 @@ +/* +fdct is a Rust translation of jfdctint.c from the +Independent JPEG Group's libjpeg version 9a +obtained from http://www.ijg.org/files/jpegsr9a.zip +It comes with the following conditions of distribution and use: + + In plain English: + + 1. We don't promise that this software works. (But if you find any bugs, + please let us know!) + 2. You can use this software for whatever you want. You don't have to pay us. + 3. You may not pretend that you wrote this software. If you use it in a + program, you must acknowledge somewhere in your documentation that + you've used the IJG code. + + In legalese: + + The authors make NO WARRANTY or representation, either express or implied, + with respect to this software, its quality, accuracy, merchantability, or + fitness for a particular purpose. This software is provided "AS IS", and you, + its user, assume the entire risk as to its quality and accuracy. + + This software is copyright (C) 1991-2014, Thomas G. Lane, Guido Vollbeding. + All Rights Reserved except as specified below. + + Permission is hereby granted to use, copy, modify, and distribute this + software (or portions thereof) for any purpose, without fee, subject to these + conditions: + (1) If any part of the source code for this software is distributed, then this + README file must be included, with this copyright and no-warranty notice + unaltered; and any additions, deletions, or changes to the original files + must be clearly indicated in accompanying documentation. + (2) If only executable code is distributed, then the accompanying + documentation must state that "this software is based in part on the work of + the Independent JPEG Group". + (3) Permission for use of this software is granted only if the user accepts + full responsibility for any undesirable consequences; the authors accept + NO LIABILITY for damages of any kind. + + These conditions apply to any software derived from or based on the IJG code, + not just to the unmodified library. If you use our work, you ought to + acknowledge us. + + Permission is NOT granted for the use of any IJG author's name or company name + in advertising or publicity relating to this software or products derived from + it. This software may be referred to only as "the Independent JPEG Group's + software". + + We specifically permit and encourage the use of this software as the basis of + commercial products, provided that all warranty or liability claims are + assumed by the product vendor. +*/ + +static CONST_BITS: i32 = 13; +static PASS1_BITS: i32 = 2; + +static FIX_0_298631336: i32 = 2446; +static FIX_0_390180644: i32 = 3196; +static FIX_0_541196100: i32 = 4433; +static FIX_0_765366865: i32 = 6270; +static FIX_0_899976223: i32 = 7373; +static FIX_1_175875602: i32 = 9633; +static FIX_1_501321110: i32 = 12_299; +static FIX_1_847759065: i32 = 15_137; +static FIX_1_961570560: i32 = 16_069; +static FIX_2_053119869: i32 = 16_819; +static FIX_2_562915447: i32 = 20_995; +static FIX_3_072711026: i32 = 25_172; + +pub(crate) fn fdct(samples: &[u8; 64], coeffs: &mut [i32; 64]) { + // Pass 1: process rows. + // Results are scaled by sqrt(8) compared to a true DCT + // furthermore we scale the results by 2**PASS1_BITS + for y in 0usize..8 { + let y0 = y * 8; + + // Even part + let t0 = i32::from(samples[y0]) + i32::from(samples[y0 + 7]); + let t1 = i32::from(samples[y0 + 1]) + i32::from(samples[y0 + 6]); + let t2 = i32::from(samples[y0 + 2]) + i32::from(samples[y0 + 5]); + let t3 = i32::from(samples[y0 + 3]) + i32::from(samples[y0 + 4]); + + let t10 = t0 + t3; + let t12 = t0 - t3; + let t11 = t1 + t2; + let t13 = t1 - t2; + + let t0 = i32::from(samples[y0]) - i32::from(samples[y0 + 7]); + let t1 = i32::from(samples[y0 + 1]) - i32::from(samples[y0 + 6]); + let t2 = i32::from(samples[y0 + 2]) - i32::from(samples[y0 + 5]); + let t3 = i32::from(samples[y0 + 3]) - i32::from(samples[y0 + 4]); + + // Apply unsigned -> signed conversion + coeffs[y0] = (t10 + t11 - 8 * 128) << PASS1_BITS as usize; + coeffs[y0 + 4] = (t10 - t11) << PASS1_BITS as usize; + + let mut z1 = (t12 + t13) * FIX_0_541196100; + // Add fudge factor here for final descale + z1 += 1 << (CONST_BITS - PASS1_BITS - 1) as usize; + + coeffs[y0 + 2] = (z1 + t12 * FIX_0_765366865) >> (CONST_BITS - PASS1_BITS) as usize; + coeffs[y0 + 6] = (z1 - t13 * FIX_1_847759065) >> (CONST_BITS - PASS1_BITS) as usize; + + // Odd part + let t12 = t0 + t2; + let t13 = t1 + t3; + + let mut z1 = (t12 + t13) * FIX_1_175875602; + // Add fudge factor here for final descale + z1 += 1 << (CONST_BITS - PASS1_BITS - 1) as usize; + + let mut t12 = t12 * (-FIX_0_390180644); + let mut t13 = t13 * (-FIX_1_961570560); + t12 += z1; + t13 += z1; + + let z1 = (t0 + t3) * (-FIX_0_899976223); + let mut t0 = t0 * FIX_1_501321110; + let mut t3 = t3 * FIX_0_298631336; + t0 += z1 + t12; + t3 += z1 + t13; + + let z1 = (t1 + t2) * (-FIX_2_562915447); + let mut t1 = t1 * FIX_3_072711026; + let mut t2 = t2 * FIX_2_053119869; + t1 += z1 + t13; + t2 += z1 + t12; + + coeffs[y0 + 1] = t0 >> (CONST_BITS - PASS1_BITS) as usize; + coeffs[y0 + 3] = t1 >> (CONST_BITS - PASS1_BITS) as usize; + coeffs[y0 + 5] = t2 >> (CONST_BITS - PASS1_BITS) as usize; + coeffs[y0 + 7] = t3 >> (CONST_BITS - PASS1_BITS) as usize; + } + + // Pass 2: process columns + // We remove the PASS1_BITS scaling but leave the results scaled up an + // overall factor of 8 + for x in (0usize..8).rev() { + // Even part + let t0 = coeffs[x] + coeffs[x + 8 * 7]; + let t1 = coeffs[x + 8] + coeffs[x + 8 * 6]; + let t2 = coeffs[x + 8 * 2] + coeffs[x + 8 * 5]; + let t3 = coeffs[x + 8 * 3] + coeffs[x + 8 * 4]; + + // Add fudge factor here for final descale + let t10 = t0 + t3 + (1 << (PASS1_BITS - 1) as usize); + let t12 = t0 - t3; + let t11 = t1 + t2; + let t13 = t1 - t2; + + let t0 = coeffs[x] - coeffs[x + 8 * 7]; + let t1 = coeffs[x + 8] - coeffs[x + 8 * 6]; + let t2 = coeffs[x + 8 * 2] - coeffs[x + 8 * 5]; + let t3 = coeffs[x + 8 * 3] - coeffs[x + 8 * 4]; + + coeffs[x] = (t10 + t11) >> PASS1_BITS as usize; + coeffs[x + 8 * 4] = (t10 - t11) >> PASS1_BITS as usize; + + let mut z1 = (t12 + t13) * FIX_0_541196100; + // Add fudge factor here for final descale + z1 += 1 << (CONST_BITS + PASS1_BITS - 1) as usize; + + coeffs[x + 8 * 2] = (z1 + t12 * FIX_0_765366865) >> (CONST_BITS + PASS1_BITS) as usize; + coeffs[x + 8 * 6] = (z1 - t13 * FIX_1_847759065) >> (CONST_BITS + PASS1_BITS) as usize; + + // Odd part + let t12 = t0 + t2; + let t13 = t1 + t3; + + let mut z1 = (t12 + t13) * FIX_1_175875602; + // Add fudge factor here for final descale + z1 += 1 << (CONST_BITS - PASS1_BITS - 1) as usize; + + let mut t12 = t12 * (-FIX_0_390180644); + let mut t13 = t13 * (-FIX_1_961570560); + t12 += z1; + t13 += z1; + + let z1 = (t0 + t3) * (-FIX_0_899976223); + let mut t0 = t0 * FIX_1_501321110; + let mut t3 = t3 * FIX_0_298631336; + t0 += z1 + t12; + t3 += z1 + t13; + + let z1 = (t1 + t2) * (-FIX_2_562915447); + let mut t1 = t1 * FIX_3_072711026; + let mut t2 = t2 * FIX_2_053119869; + t1 += z1 + t13; + t2 += z1 + t12; + + coeffs[x + 8] = t0 >> (CONST_BITS + PASS1_BITS) as usize; + coeffs[x + 8 * 3] = t1 >> (CONST_BITS + PASS1_BITS) as usize; + coeffs[x + 8 * 5] = t2 >> (CONST_BITS + PASS1_BITS) as usize; + coeffs[x + 8 * 7] = t3 >> (CONST_BITS + PASS1_BITS) as usize; + } +} |