mirror of https://github.com/opencv/opencv.git
Open Source Computer Vision Library
https://opencv.org/
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
248 lines
8.0 KiB
248 lines
8.0 KiB
#ifndef INCLUDED_IMF_RGBA_YCA_H |
|
#define INCLUDED_IMF_RGBA_YCA_H |
|
|
|
////////////////////////////////////////////////////////////////////////////// |
|
// |
|
// Copyright (c) 2004, Industrial Light & Magic, a division of Lucasfilm |
|
// Entertainment Company Ltd. Portions contributed and copyright held by |
|
// others as indicated. All rights reserved. |
|
// |
|
// Redistribution and use in source and binary forms, with or without |
|
// modification, are permitted provided that the following conditions are |
|
// met: |
|
// |
|
// * Redistributions of source code must retain the above |
|
// copyright notice, this list of conditions and the following |
|
// disclaimer. |
|
// |
|
// * Redistributions in binary form must reproduce the above |
|
// copyright notice, this list of conditions and the following |
|
// disclaimer in the documentation and/or other materials provided with |
|
// the distribution. |
|
// |
|
// * Neither the name of Industrial Light & Magic nor the names of |
|
// any other contributors to this software may be used to endorse or |
|
// promote products derived from this software without specific prior |
|
// written permission. |
|
// |
|
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS |
|
// IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, |
|
// THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR |
|
// PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR |
|
// CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, |
|
// EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, |
|
// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR |
|
// PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF |
|
// LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING |
|
// NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS |
|
// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
|
// |
|
////////////////////////////////////////////////////////////////////////////// |
|
|
|
//----------------------------------------------------------------------------- |
|
// |
|
// Conversion between RGBA (red, green, blue alpha) |
|
// and YCA (luminance, subsampled chroma, alpha) data: |
|
// |
|
// Luminance, Y, is computed as a weighted sum of R, G, and B: |
|
// |
|
// Y = yw.x * R + yw.y * G + yw.z * B |
|
// |
|
// Function computeYw() computes a set of RGB-to-Y weights, yw, |
|
// from a set of primary and white point chromaticities. |
|
// |
|
// Chroma, C, consists of two components, RY and BY: |
|
// |
|
// RY = (R - Y) / Y |
|
// BY = (B - Y) / Y |
|
// |
|
// For efficiency, the x and y subsampling rates for chroma are |
|
// hardwired to 2, and the chroma subsampling and reconstruction |
|
// filters are fixed 27-pixel wide windowed sinc functions. |
|
// |
|
// Starting with an image that has RGBA data for all pixels, |
|
// |
|
// RGBA RGBA RGBA RGBA ... RGBA RGBA |
|
// RGBA RGBA RGBA RGBA ... RGBA RGBA |
|
// RGBA RGBA RGBA RGBA ... RGBA RGBA |
|
// RGBA RGBA RGBA RGBA ... RGBA RGBA |
|
// ... |
|
// RGBA RGBA RGBA RGBA ... RGBA RGBA |
|
// RGBA RGBA RGBA RGBA ... RGBA RGBA |
|
// |
|
// function RGBAtoYCA() converts the pixels to YCA format: |
|
// |
|
// YCA YCA YCA YCA ... YCA YCA |
|
// YCA YCA YCA YCA ... YCA YCA |
|
// YCA YCA YCA YCA ... YCA YCA |
|
// YCA YCA YCA YCA ... YCA YCA |
|
// ... |
|
// YCA YCA YCA YCA ... YCA YCA |
|
// YCA YCA YCA YCA ... YCA YCA |
|
// |
|
// Next, decimateChomaHoriz() eliminates the chroma values from |
|
// the odd-numbered pixels in every scan line: |
|
// |
|
// YCA YA YCA YA ... YCA YA |
|
// YCA YA YCA YA ... YCA YA |
|
// YCA YA YCA YA ... YCA YA |
|
// YCA YA YCA YA ... YCA YA |
|
// ... |
|
// YCA YA YCA YA ... YCA YA |
|
// YCA YA YCA YA ... YCA YA |
|
// |
|
// decimateChromaVert() eliminates all chroma values from the |
|
// odd-numbered scan lines: |
|
// |
|
// YCA YA YCA YA ... YCA YA |
|
// YA YA YA YA ... YA YA |
|
// YCA YA YCA YA ... YCA YA |
|
// YA YA YA YA ... YA YA |
|
// ... |
|
// YCA YA YCA YA ... YCA YA |
|
// YA YA YA YA ... YA YA |
|
// |
|
// Finally, roundYCA() reduces the precision of the luminance |
|
// and chroma values so that the pixel data shrink more when |
|
// they are saved in a compressed file. |
|
// |
|
// The output of roundYCA() can be converted back to a set |
|
// of RGBA pixel data that is visually very similar to the |
|
// original RGBA image, by calling reconstructChromaHoriz(), |
|
// reconstructChromaVert(), YCAtoRGBA(), and finally |
|
// fixSaturation(). |
|
// |
|
//----------------------------------------------------------------------------- |
|
|
|
#include <ImfRgba.h> |
|
#include <ImfChromaticities.h> |
|
|
|
namespace Imf { |
|
namespace RgbaYca { |
|
|
|
|
|
// |
|
// Width of the chroma subsampling and reconstruction filters |
|
// |
|
|
|
static const int N = 27; |
|
static const int N2 = N / 2; |
|
|
|
|
|
// |
|
// Convert a set of primary chromaticities into a set of weighting |
|
// factors for computing a pixels's luminance, Y, from R, G and B |
|
// |
|
|
|
Imath::V3f computeYw (const Chromaticities &cr); |
|
|
|
|
|
// |
|
// Convert an array of n RGBA pixels, rgbaIn, to YCA (luminance/chroma/alpha): |
|
// |
|
// ycaOut[i].g = Y (rgbaIn[i]); |
|
// ycaOut[i].r = RY (rgbaIn[i]); |
|
// ycaOut[i].b = BY (rgbaIn[i]); |
|
// ycaOut[i].a = aIsValid? rgbaIn[i].a: 1 |
|
// |
|
// yw is a set of RGB-to-Y weighting factors, as computed by computeYw(). |
|
// |
|
|
|
void RGBAtoYCA (const Imath::V3f &yw, |
|
int n, |
|
bool aIsValid, |
|
const Rgba rgbaIn[/*n*/], |
|
Rgba ycaOut[/*n*/]); |
|
|
|
// |
|
// Perform horizontal low-pass filtering and subsampling of |
|
// the chroma channels of an array of n pixels. In order |
|
// to avoid indexing off the ends of the input array during |
|
// low-pass filtering, ycaIn must have N2 extra pixels at |
|
// both ends. Before calling decimateChromaHoriz(), the extra |
|
// pixels should be filled with copies of the first and last |
|
// "real" input pixel. |
|
// |
|
|
|
void decimateChromaHoriz (int n, |
|
const Rgba ycaIn[/*n+N-1*/], |
|
Rgba ycaOut[/*n*/]); |
|
|
|
// |
|
// Perform vertical chroma channel low-pass filtering and subsampling. |
|
// N scan lines of input pixels are combined into a single scan line |
|
// of output pixels. |
|
// |
|
|
|
void decimateChromaVert (int n, |
|
const Rgba * const ycaIn[N], |
|
Rgba ycaOut[/*n*/]); |
|
|
|
// |
|
// Round the luminance and chroma channels of an array of YCA |
|
// pixels that has already been filtered and subsampled. |
|
// The signifcands of the pixels' luminance and chroma values |
|
// are rounded to roundY and roundC bits respectively. |
|
// |
|
|
|
void roundYCA (int n, |
|
unsigned int roundY, |
|
unsigned int roundC, |
|
const Rgba ycaIn[/*n*/], |
|
Rgba ycaOut[/*n*/]); |
|
|
|
// |
|
// For a scan line that has valid chroma data only for every other pixel, |
|
// reconstruct the missing chroma values. |
|
// |
|
|
|
void reconstructChromaHoriz (int n, |
|
const Rgba ycaIn[/*n+N-1*/], |
|
Rgba ycaOut[/*n*/]); |
|
|
|
// |
|
// For a scan line that has only luminance and no valid chroma data, |
|
// reconstruct chroma from the surronding N scan lines. |
|
// |
|
|
|
void reconstructChromaVert (int n, |
|
const Rgba * const ycaIn[N], |
|
Rgba ycaOut[/*n*/]); |
|
|
|
// |
|
// Convert an array of n YCA (luminance/chroma/alpha) pixels to RGBA. |
|
// This function is the inverse of RGBAtoYCA(). |
|
// yw is a set of RGB-to-Y weighting factors, as computed by computeYw(). |
|
// |
|
|
|
void YCAtoRGBA (const Imath::V3f &yw, |
|
int n, |
|
const Rgba ycaIn[/*n*/], |
|
Rgba rgbaOut[/*n*/]); |
|
|
|
// |
|
// Eliminate super-saturated pixels: |
|
// |
|
// Converting an image from RGBA to YCA, low-pass filtering chroma, |
|
// and converting the result back to RGBA can produce pixels with |
|
// super-saturated colors, where one or two of the RGB components |
|
// become zero or negative. (The low-pass and reconstruction filters |
|
// introduce some amount of ringing into the chroma components. |
|
// This can lead to negative RGB values near high-contrast edges.) |
|
// |
|
// The fixSaturation() function finds super-saturated pixels and |
|
// corrects them by desaturating their colors while maintaining |
|
// their luminance. fixSaturation() takes three adjacent input |
|
// scan lines, rgbaIn[0], rgbaIn[1], rgbaIn[2], adjusts the |
|
// saturation of rgbaIn[1], and stores the result in rgbaOut. |
|
// |
|
|
|
void fixSaturation (const Imath::V3f &yw, |
|
int n, |
|
const Rgba * const rgbaIn[3], |
|
Rgba rgbaOut[/*n*/]); |
|
|
|
} // namespace RgbaYca |
|
} // namespace Imf |
|
|
|
#endif
|
|
|