diff --git a/Cargo.toml b/Cargo.toml index aa88c9ea0d..379cd3d6a2 100644 --- a/Cargo.toml +++ b/Cargo.toml @@ -114,4 +114,4 @@ harness = false [[bench]] path = "benches/blur.rs" name = "blur" -harness = false +harness = false \ No newline at end of file diff --git a/src/codecs/jpeg/encoder.rs b/src/codecs/jpeg/encoder.rs index d641b44bb2..0c1f074985 100644 --- a/src/codecs/jpeg/encoder.rs +++ b/src/codecs/jpeg/encoder.rs @@ -1,8 +1,5 @@ #![allow(clippy::too_many_arguments)] -use std::borrow::Cow; -use std::io::{self, Write}; - use crate::error::{ ImageError, ImageResult, ParameterError, ParameterErrorKind, UnsupportedError, UnsupportedErrorKind, @@ -10,6 +7,9 @@ use crate::error::{ use crate::image::{ImageEncoder, ImageFormat}; use crate::utils::clamp; use crate::{ExtendedColorType, GenericImageView, ImageBuffer, Luma, Pixel, Rgb}; +use num_traits::ToPrimitive; +use std::borrow::Cow; +use std::io::{self, Write}; use super::entropy::build_huff_lut_const; use super::transform; @@ -771,19 +771,36 @@ fn encode_coefficient(coefficient: i32) -> (u8, u16) { #[inline] fn rgb_to_ycbcr(pixel: P) -> (u8, u8, u8) { - use crate::traits::Primitive; - use num_traits::cast::ToPrimitive; - let [r, g, b] = pixel.to_rgb().0; - let max: f32 = P::Subpixel::DEFAULT_MAX_VALUE.to_f32().unwrap(); - let r: f32 = r.to_f32().unwrap(); - let g: f32 = g.to_f32().unwrap(); - let b: f32 = b.to_f32().unwrap(); - - // Coefficients from JPEG File Interchange Format (Version 1.02), multiplied for 255 maximum. - let y = 76.245 / max * r + 149.685 / max * g + 29.07 / max * b; - let cb = -43.0185 / max * r - 84.4815 / max * g + 127.5 / max * b + 128.; - let cr = 127.5 / max * r - 106.7685 / max * g - 20.7315 / max * b + 128.; + let r: i32 = r.to_u8().unwrap() as i32; + let g: i32 = g.to_u8().unwrap() as i32; + let b: i32 = b.to_u8().unwrap() as i32; + + /* + JPEG RGB -> YCbCr is defined as following equations using Bt.601 Full Range matrix: + Y = 0.29900 * R + 0.58700 * G + 0.11400 * B + Cb = -0.16874 * R - 0.33126 * G + 0.50000 * B + 128 + Cr = 0.50000 * R - 0.41869 * G - 0.08131 * B + 128 + + To avoid using slow floating point conversion is done in fixed point, + using following coefficients with rounding to nearest integer mode: + */ + + const C_YR: i32 = 19595; // 0.29900 = 19595 * 2^-16 + const C_YG: i32 = 38469; // 0.58700 = 38469 * 2^-16 + const C_YB: i32 = 7471; // 0.11400 = 7471 * 2^-16 + const Y_ROUNDING: i32 = (1 << 15) - 1; // + 0.5 to perform rounding shift right in-place + const C_UR: i32 = 11059; // 0.16874 = 11059 * 2^-16 + const C_UG: i32 = 21709; // 0.33126 = 21709 * 2^-16 + const C_UB: i32 = 32768; // 0.5 = 32768 * 2^-16 + const UV_BIAS_ROUNDING: i32 = (128 * (1 << 16)) + ((1 << 15) - 1); // 128 + 0.5 = ((128 * (1 << 16)) + ((1 << 15) - 1)) * 2^-16 ; + 0.5 to perform rounding shift right in-place + const C_VR: i32 = C_UB; // 0.5 = 32768 * 2^-16 + const C_VG: i32 = 27439; // 0.41869 = 27439 * 2^-16 + const C_VB: i32 = 5329; // 0.08131409 = 5329 * 2^-16 + + let y = (C_YR * r + C_YG * g + C_YB * b + Y_ROUNDING) >> 16; + let cb = (-C_UR * r - C_UG * g + C_UB * b + UV_BIAS_ROUNDING) >> 16; + let cr = (C_VR * r - C_VG * g - C_VB * b + UV_BIAS_ROUNDING) >> 16; (y as u8, cb as u8, cr as u8) }