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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/*
* This file is part of the LibreOffice project.
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/.
*/
/* TODO Use textureOffset for newest version of GLSL */
#version 130
uniform sampler2D crc_table;
uniform sampler2D sampler;
uniform float xstep;
uniform float ystep;
varying vec2 tex_coord;
const int scale = 4;
const float ratio = 16.0;
ivec2 crc64( ivec2 hval, int color )
{
int dx = 2 * ((hval[0] ^ color) & 0xff);
float s = dx / 255.0;
vec4 table_value_lo = round(texture2D( crc_table, vec2( s, 0.0 ) ) * 255.0);
s = (dx+1) / 255.0;
vec4 table_value_hi = round(texture2D( crc_table, vec2( s, 0.0 ) ) * 255.0);
int tvalue_lo = int(table_value_lo[0]) | (int(table_value_lo[1]) << 8) | (int(table_value_lo[2]) << 16) | (int(table_value_lo[3]) << 24);
int tvalue_hi = int(table_value_hi[0]) | (int(table_value_hi[1]) << 8) | (int(table_value_hi[2]) << 16) | (int(table_value_hi[3]) << 24);
hval[1] = tvalue_hi ^ (hval[1] >> 8);
hval[0] = tvalue_lo ^ ( (hval[1] << 24) | (hval[0] >> 8) );
return hval;
}
void main(void)
{
ivec2 Crc = ivec2( 0xffffffff, 0xffffffff );
vec2 offset = vec2( 0.0, 0.0 );
vec2 next_coord = tex_coord.st;
for( int y = 0; y < scale && next_coord.y <= 1.0; ++y )
{
for( int x = 0; x < scale && next_coord.x <= 1.0; ++x )
{
vec4 pixel = round(texture2D( sampler, next_coord ) * 255.0);
int r = int(pixel.r); // 0..255
int g = int(pixel.g); // 0..255
int b = int(pixel.b); // 0..255
int a = int(pixel.a); // 0..255
Crc = crc64( Crc, r );
Crc = crc64( Crc, g );
Crc = crc64( Crc, b );
Crc = crc64( Crc, a );
offset.x += xstep;
next_coord = tex_coord.st + offset;
}
offset.y += ystep;
offset.x = 0.0;
next_coord = tex_coord.st + offset;
}
Crc[0] = ~Crc[0];
Crc[1] = ~Crc[1];
int Hash = Crc[0] ^ Crc[1];
float fr = ( Hash & 0xff) / 255.0;
float fg = ((Hash >> 8) & 0xff) / 255.0;
float fb = ((Hash >> 16) & 0xff) / 255.0;
float fa = ((Hash >> 24) & 0xff) / 255.0;
gl_FragColor = vec4(fr, fg, fb, fa);
}
/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
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