forked from AuroraMiddleware/gtk
280 lines
7.1 KiB
C
280 lines
7.1 KiB
C
/*
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* Copyright (C) 2012 Canonical Ltd
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free
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* Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
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* MA 02110-1301, USA.
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*
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* Authored by Andrea Cimitan <andrea.cimitan@canonical.com>
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* Original code from Mirco Mueller <mirco.mueller@canonical.com>
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*
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*/
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#include "gtkcairoblurprivate.h"
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#include <math.h>
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/*
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* Notes:
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* based on exponential-blur algorithm by Jani Huhtanen
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*/
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static inline void
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_blurinner (guchar* pixel,
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gint *zR,
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gint *zG,
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gint *zB,
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gint *zA,
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gint alpha,
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gint aprec,
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gint zprec)
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{
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gint R;
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gint G;
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gint B;
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guchar A;
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R = *pixel;
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G = *(pixel + 1);
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B = *(pixel + 2);
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A = *(pixel + 3);
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*zR += (alpha * ((R << zprec) - *zR)) >> aprec;
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*zG += (alpha * ((G << zprec) - *zG)) >> aprec;
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*zB += (alpha * ((B << zprec) - *zB)) >> aprec;
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*zA += (alpha * ((A << zprec) - *zA)) >> aprec;
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*pixel = *zR >> zprec;
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*(pixel + 1) = *zG >> zprec;
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*(pixel + 2) = *zB >> zprec;
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*(pixel + 3) = *zA >> zprec;
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}
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static inline void
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_blurrow (guchar* pixels,
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gint width,
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gint height,
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gint rowstride,
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gint channels,
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gint line,
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gint alpha,
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gint aprec,
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gint zprec)
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{
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gint zR;
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gint zG;
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gint zB;
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gint zA;
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gint index;
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guchar* scanline;
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scanline = &pixels[line * rowstride];
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zR = *scanline << zprec;
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zG = *(scanline + 1) << zprec;
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zB = *(scanline + 2) << zprec;
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zA = *(scanline + 3) << zprec;
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for (index = 0; index < width; index ++)
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_blurinner (&scanline[index * channels],
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&zR,
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&zG,
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&zB,
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&zA,
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alpha,
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aprec,
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zprec);
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for (index = width - 2; index >= 0; index--)
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_blurinner (&scanline[index * channels],
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&zR,
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&zG,
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&zB,
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&zA,
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alpha,
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aprec,
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zprec);
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}
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static inline void
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_blurcol (guchar* pixels,
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gint width,
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gint height,
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gint rowstride,
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gint channels,
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gint x,
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gint alpha,
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gint aprec,
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gint zprec)
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{
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gint zR;
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gint zG;
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gint zB;
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gint zA;
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gint index;
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guchar* ptr;
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ptr = pixels;
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ptr += x * channels;
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zR = *((guchar*) ptr ) << zprec;
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zG = *((guchar*) ptr + 1) << zprec;
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zB = *((guchar*) ptr + 2) << zprec;
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zA = *((guchar*) ptr + 3) << zprec;
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for (index = 0; index < height; index++)
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_blurinner (&ptr[index * rowstride],
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&zR,
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&zG,
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&zB,
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&zA,
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alpha,
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aprec,
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zprec);
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for (index = height - 2; index >= 0; index--)
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_blurinner (&ptr[index * rowstride],
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&zR,
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&zG,
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&zB,
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&zA,
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alpha,
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aprec,
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zprec);
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}
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/*
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* _expblur:
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* @pixels: image data
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* @width: image width
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* @height: image height
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* @rowstride: image rowstride
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* @channels: image channels
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* @radius: kernel radius
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* @aprec: precision of alpha parameter in fixed-point format 0.aprec
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* @zprec: precision of state parameters zR,zG,zB and zA in fp format 8.zprec
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*
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* Performs an in-place blur of image data “pixels”
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* with kernel of approximate radius “radius”.
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*
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* Blurs with two sided exponential impulse response.
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*
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*/
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static void
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_expblur (guchar* pixels,
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gint width,
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gint height,
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gint rowstride,
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gint channels,
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double radius,
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gint aprec,
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gint zprec)
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{
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gint alpha;
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int row, col;
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/* Calculate the alpha such that 90% of
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* the kernel is within the radius.
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* (Kernel extends to infinity) */
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alpha = (gint) ((1 << aprec) * (1.0f - expf (-2.3f / (radius + 1.f))));
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for (row = 0; row < height; row++)
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_blurrow (pixels,
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width,
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height,
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rowstride,
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channels,
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row,
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alpha,
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aprec,
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zprec);
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for(col = 0; col < width; col++)
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_blurcol (pixels,
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width,
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height,
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rowstride,
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channels,
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col,
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alpha,
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aprec,
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zprec);
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}
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/*
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* _gtk_cairo_blur_surface:
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* @surface: a cairo image surface.
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* @radius: the blur radius.
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*
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* Blurs the cairo image surface at the given radius.
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*/
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void
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_gtk_cairo_blur_surface (cairo_surface_t* surface,
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double radius)
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{
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cairo_format_t format;
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g_return_if_fail (surface != NULL);
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g_return_if_fail (cairo_surface_get_type (surface) == CAIRO_SURFACE_TYPE_IMAGE);
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format = cairo_image_surface_get_format (surface);
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g_return_if_fail (format == CAIRO_FORMAT_RGB24 ||
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format == CAIRO_FORMAT_ARGB32);
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if (radius == 0)
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return;
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/* Before we mess with the surface execute any pending drawing. */
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cairo_surface_flush (surface);
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_expblur (cairo_image_surface_get_data (surface),
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cairo_image_surface_get_width (surface),
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cairo_image_surface_get_height (surface),
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cairo_image_surface_get_stride (surface),
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4,
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radius,
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16,
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7);
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/* Inform cairo we altered the surfaces contents. */
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cairo_surface_mark_dirty (surface);
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}
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/**
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* _gtk_cairo_blur_compute_pixels:
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* @radius: the radius to compute the pixels for
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*
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* Computes the number of pixels necessary to extend an image in one
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* direction to hold the image with shadow.
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*
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* This is just the number of pixels added by the blur radius, shadow
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* offset and spread are not included.
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*
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* Much of this, the 3 * sqrt(2 * pi) / 4, is the known value for
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* approximating a Gaussian using box blurs. This yields quite a good
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* approximation for a Gaussian. Then we multiply this by 1.5 since our
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* code wants the radius of the entire triple-box-blur kernel instead of
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* the diameter of an individual box blur. For more details, see:
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* http://www.w3.org/TR/SVG11/filters.html#feGaussianBlurElement
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* https://bugzilla.mozilla.org/show_bug.cgi?id=590039#c19
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*/
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#define GAUSSIAN_SCALE_FACTOR ((3.0 * sqrt(2 * G_PI) / 4) * 1.5)
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int
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_gtk_cairo_blur_compute_pixels (double radius)
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{
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return floor (radius * GAUSSIAN_SCALE_FACTOR + 0.5);
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}
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