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/*
* Copyright (C) 2013 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "ip.rsh"
int height;
int width;
static int radius;
rs_allocation InPixel;
rs_allocation ScratchPixel1;
rs_allocation ScratchPixel2;
const int MAX_RADIUS = 25;
// Store our coefficients here
static float gaussian[MAX_RADIUS * 2 + 1];
void setRadius(int rad) {
radius = rad;
// Compute gaussian weights for the blur
// e is the euler's number
float e = 2.718281828459045f;
float pi = 3.1415926535897932f;
// g(x) = ( 1 / sqrt( 2 * pi ) * sigma) * e ^ ( -x^2 / 2 * sigma^2 )
// x is of the form [-radius .. 0 .. radius]
// and sigma varies with radius.
// Based on some experimental radius values and sigma's
// we approximately fit sigma = f(radius) as
// sigma = radius * 0.4 + 0.6
// The larger the radius gets, the more our gaussian blur
// will resemble a box blur since with large sigma
// the gaussian curve begins to lose its shape
float sigma = 0.4f * (float)radius + 0.6f;
// Now compute the coefficints
// We will store some redundant values to save some math during
// the blur calculations
// precompute some values
float coeff1 = 1.0f / (sqrt( 2.0f * pi ) * sigma);
float coeff2 = - 1.0f / (2.0f * sigma * sigma);
float normalizeFactor = 0.0f;
float floatR = 0.0f;
for (int r = -radius; r <= radius; r ++) {
floatR = (float)r;
gaussian[r + radius] = coeff1 * pow(e, floatR * floatR * coeff2);
normalizeFactor += gaussian[r + radius];
}
//Now we need to normalize the weights because all our coefficients need to add up to one
normalizeFactor = 1.0f / normalizeFactor;
for (int r = -radius; r <= radius; r ++) {
floatR = (float)r;
gaussian[r + radius] *= normalizeFactor;
}
}
float4 __attribute__((kernel)) copyIn(uchar4 in) {
return convert_float4(in);
}
uchar4 __attribute__((kernel)) vert(uint32_t x, uint32_t y) {
float3 blurredPixel = 0;
int gi = 0;
uchar4 out;
if ((y > radius) && (y < (height - radius))) {
for (int r = -radius; r <= radius; r ++) {
float4 i = rsGetElementAt_float4(ScratchPixel2, x, y + r);
blurredPixel += i.xyz * gaussian[gi++];
}
} else {
for (int r = -radius; r <= radius; r ++) {
int validH = rsClamp((int)y + r, (int)0, (int)(height - 1));
float4 i = rsGetElementAt_float4(ScratchPixel2, x, validH);
blurredPixel += i.xyz * gaussian[gi++];
}
}
out.xyz = convert_uchar3(clamp(blurredPixel, 0.f, 255.f));
out.w = 0xff;
return out;
}
float4 __attribute__((kernel)) horz(uint32_t x, uint32_t y) {
float4 blurredPixel = 0;
int gi = 0;
if ((x > radius) && (x < (width - radius))) {
for (int r = -radius; r <= radius; r ++) {
float4 i = rsGetElementAt_float4(ScratchPixel1, x + r, y);
blurredPixel += i * gaussian[gi++];
}
} else {
for (int r = -radius; r <= radius; r ++) {
// Stepping left and right away from the pixel
int validX = rsClamp((int)x + r, (int)0, (int)(width - 1));
float4 i = rsGetElementAt_float4(ScratchPixel1, validX, y);
blurredPixel += i * gaussian[gi++];
}
}
return blurredPixel;
}
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