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Diffstat (limited to 'src/plugins/graphicssystems/meego/dithering.cpp')
| -rw-r--r-- | src/plugins/graphicssystems/meego/dithering.cpp | 266 |
1 files changed, 266 insertions, 0 deletions
diff --git a/src/plugins/graphicssystems/meego/dithering.cpp b/src/plugins/graphicssystems/meego/dithering.cpp new file mode 100644 index 0000000000..2561c22ff6 --- /dev/null +++ b/src/plugins/graphicssystems/meego/dithering.cpp @@ -0,0 +1,266 @@ +/**************************************************************************** +** +** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies). +** All rights reserved. +** Contact: Nokia Corporation (qt-info@nokia.com) +** +** This file is part of the plugins of the Qt Toolkit. +** +** $QT_BEGIN_LICENSE:LGPL$ +** No Commercial Usage +** This file contains pre-release code and may not be distributed. +** You may use this file in accordance with the terms and conditions +** contained in the Technology Preview License Agreement accompanying +** this package. +** +** GNU Lesser General Public License Usage +** Alternatively, this file may be used under the terms of the GNU Lesser +** General Public License version 2.1 as published by the Free Software +** Foundation and appearing in the file LICENSE.LGPL included in the +** packaging of this file. Please review the following information to +** ensure the GNU Lesser General Public License version 2.1 requirements +** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html. +** +** In addition, as a special exception, Nokia gives you certain additional +** rights. These rights are described in the Nokia Qt LGPL Exception +** version 1.1, included in the file LGPL_EXCEPTION.txt in this package. +** +** If you have questions regarding the use of this file, please contact +** Nokia at qt-info@nokia.com. +** +** +** +** +** +** +** +** +** $QT_END_LICENSE$ +** +****************************************************************************/ + +// Implements two dithering methods: +// +// * convertRGBA32_to_RGB565 +// +// This is implemented using Ordered Bayer Dithering. The code has been adapted +// from QX11PixmapData::fromImage. This method was originally implemented using +// Floyd-Steinberg dithering but was later changed to Ordered Dithering because +// of the better quality of the results. +// +// * convertRGBA32_to_RGBA4444 +// +// This is implemented using Floyd-Steinberg dithering. +// +// The alghorithm used here is not the fastest possible but it's prolly fast enough: +// uses look-up tables, integer-only arthmetics and works in one pass on two lines +// at a time. It's a high-quality dithering using 1/8 diffusion precission. +// Each channel (RGBA) is diffused independently and alpha is dithered too. + +#include <string.h> +#include <stdio.h> +#include <stdlib.h> +#include <math.h> +#include <QVarLengthArray> + +// Gets a component (red = 1, green = 2...) from a RGBA data structure. +// data is unsigned char. stride is the number of bytes per line. +#define GET_RGBA_COMPONENT(data, x, y, stride, c) (data[(y * stride) + (x << 2) + c]) + +// Writes a new pixel with r, g, b to data in 565 16bit format. Data is a short. +#define PUT_565(data, x, y, width, r, g, b) (data[(y * width) + x] = (r << 11) | (g << 5) | b) + +// Writes a new pixel with r, g, b, a to data in 4444 RGBA 16bit format. Data is a short. +#define PUT_4444(data, x, y, width, r, g, b, a) (data[(y * width) + x] = (r << 12) | (g << 8) | (b << 4) | a) + +// Writes(ads) a new value to the diffusion accumulator. accumulator is a short. +// x, y is a position in the accumulation buffer. y can be 0 or 1 -- we operate on two lines at time. +#define ACCUMULATE(accumulator, x, y, width, v) if (x < width && x >= 0) accumulator[(y * width) + x] += v + +// Clamps a value to be in 0..255 range. +#define CLAMP_256(v) if (v > 255) v = 255; if (v < 0) v = 0; + +// Converts incoming RGB32 (QImage::Format_RGB32) to RGB565. Returns the newly allocated data. +unsigned short* convertRGB32_to_RGB565(const unsigned char *in, int width, int height, int stride) +{ + static bool thresholdMapInitialized = false; + static int thresholdMap[16][16]; + + if (!thresholdMapInitialized) { + int i; + int j; + int n; + + thresholdMap[0][0] = 0; + thresholdMap[1][0] = 2; + thresholdMap[0][1] = 3; + thresholdMap[1][1] = 1; + + for (n=2; n<16; n*=2) { + for (i=0; i<n; i++) { + for (j=0; j<n; j++) { + thresholdMap[i][j] *= 4; + thresholdMap[i+n][j] = thresholdMap[i][j] + 2; + thresholdMap[i][j+n] = thresholdMap[i][j] + 3; + thresholdMap[i+n][j+n] = thresholdMap[i][j] + 1; + } + } + } + + thresholdMapInitialized = true; + } + + // Output line stride. Aligned to 4 bytes. + int alignedWidth = width; + if (alignedWidth % 2 > 0) + alignedWidth++; + + // Will store output + unsigned short *out = (unsigned short *)malloc (alignedWidth * height * 2); + + int x; + int y; + int threshold; + + // For each line... + for (y = 0; y < height; y++) { + + // For each column.... + for (x = 0; x < width; x++) { + + int r = GET_RGBA_COMPONENT(in, x, y, stride, 0); + int g = GET_RGBA_COMPONENT(in, x, y, stride, 1); + int b = GET_RGBA_COMPONENT(in, x, y, stride, 2); + + threshold = thresholdMap[x%16][y%16]; + + if (r <= (255-(1<<3)) && ((r<<5) & 255) > threshold) r += (1<<3); + if (g <= (255-(1<<2)) && ((g<<6) & 255) > threshold) g += (1<<2); + if (b <= (255-(1<<3)) && ((b<<5) & 255) > threshold) b += (1<<3); + + // Write the newly produced pixel + PUT_565(out, x, y, alignedWidth, ((b >> 3) & 0x1f), ((g >> 2) & 0x3f), ((r >> 3) & 0x1f)); + } + } + + return out; +} + +// Converts incoming RGBA32 (QImage::Format_ARGB32_Premultiplied) to RGB565. Returns the newly allocated data. +// This function is similar (yet different) to the _565 variant but it makes sense to duplicate it here for simplicity. +// The output has each scan line aligned to 4 bytes (as expected by GL by default). +unsigned short* convertARGB32_to_RGBA4444(const unsigned char *in, int width, int height, int stride) +{ + // Output line stride. Aligned to 4 bytes. + int alignedWidth = width; + if (alignedWidth % 2 > 0) + alignedWidth++; + + // Will store output + unsigned short *out = (unsigned short *) malloc(alignedWidth * 2 * height); + + // Lookup tables for the 8bit => 4bit conversion + unsigned char lookup_8bit_to_4bit[256]; + short lookup_8bit_to_4bit_diff[256]; + + // Macros for the conversion using the lookup table. + #define CONVERT_8BIT_TO_4BIT(v) (lookup_8bit_to_4bit[v]) + #define DIFF_8BIT_TO_4BIT(v) (lookup_8bit_to_4bit_diff[v]) + + int i; + int x, y, c; // Pixel we're processing. c is component number (0, 1, 2, 3 for r, b, b, a) + short component[4]; // Stores the new components (r, g, b, a) for pixel produced during conversion + short diff; // The difference between the converted value and the original one. To be accumulated. + QVarLengthArray <short> accumulatorData(4 * width * 2); // Data for three acumulators for r, g, b. Each accumulator is two lines. + short *accumulator[4]; // Helper for accessing the accumulator on a per-channel basis more easily. + accumulator[0] = accumulatorData.data(); + accumulator[1] = accumulatorData.data() + width; + accumulator[2] = accumulatorData.data() + (width * 2); + accumulator[3] = accumulatorData.data() + (width * 3); + + // Produce the conversion lookup tables. + for (i = 0; i < 256; i++) { + lookup_8bit_to_4bit[i] = round(i / 16.0); + // Before bitshifts: (i * 8) - (... * 16 * 8) + lookup_8bit_to_4bit_diff[i] = (i << 3) - (lookup_8bit_to_4bit[i] << 7); + + if (lookup_8bit_to_4bit[i] > 15) + lookup_8bit_to_4bit[i] = 15; + } + + // Clear the accumulators + memset(accumulator[0], 0, width * 4); + memset(accumulator[1], 0, width * 4); + memset(accumulator[2], 0, width * 4); + memset(accumulator[3], 0, width * 4); + + // For each line... + for (y = 0; y < height; y++) { + + // For each component (r, g, b, a)... + memcpy(accumulator[0], accumulator[0] + width, width * 2); + memset(accumulator[0] + width, 0, width * 2); + + memcpy(accumulator[1], accumulator[1] + width, width * 2); + memset(accumulator[1] + width, 0, width * 2); + + memcpy(accumulator[2], accumulator[2] + width, width * 2); + memset(accumulator[2] + width, 0, width * 2); + + memcpy(accumulator[3], accumulator[3] + width, width * 2); + memset(accumulator[3] + width, 0, width * 2); + + // For each column.... + for (x = 0; x < width; x++) { + + // For each component (r, g, b, a)... + for (c = 0; c < 4; c++) { + + // Get the 8bit value from the original image + component[c] = GET_RGBA_COMPONENT(in, x, y, stride, c); + + // Add the diffusion for this pixel we stored in the accumulator. + // >> 7 because the values in accumulator are stored * 128 + component[c] += accumulator[c][x] >> 7; + + // Make sure we're not over the boundaries. + CLAMP_256(component[c]); + + // Store the difference from converting 8bit => 4bit and the orig pixel. + // Convert 8bit => 4bit. + diff = DIFF_8BIT_TO_4BIT(component[c]); + component[c] = CONVERT_8BIT_TO_4BIT(component[c]); + + // Distribute the difference according to the matrix in the + // accumulation bufffer. + ACCUMULATE(accumulator[c], x + 1, 0, width, diff * 7); + ACCUMULATE(accumulator[c], x - 1, 1, width, diff * 3); + ACCUMULATE(accumulator[c], x, 1, width, diff * 5); + ACCUMULATE(accumulator[c], x + 1, 1, width, diff * 1); + } + + // Write the newly produced pixel + PUT_4444(out, x, y, alignedWidth, component[0], component[1], component[2], component[3]); + } + } + + return out; +} + +unsigned char* convertBGRA32_to_RGBA32(const unsigned char *in, int width, int height, int stride) +{ + unsigned char *out = (unsigned char *) malloc(stride * height); + + // For each line... + for (int y = 0; y < height; y++) { + // For each column + for (int x = 0; x < width; x++) { + out[(stride * y) + (x * 4) + 0] = in[(stride * y) + (x * 4) + 2]; + out[(stride * y) + (x * 4) + 1] = in[(stride * y) + (x * 4) + 1]; + out[(stride * y) + (x * 4) + 2] = in[(stride * y) + (x * 4) + 0]; + out[(stride * y) + (x * 4) + 3] = in[(stride * y) + (x * 4) + 3]; + } + } + + return out; +} |