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#define ANGLE_PRIME 95273
#define RADIUS_PRIME 29537
void sample_min_max(const __global float4 *src_buf,
int src_width,
int src_height,
const __global float *radiuses,
const __global float *lut_cos,
const __global float *lut_sin,
int x,
int y,
int radius,
int samples,
float4 *min,
float4 *max,
int j,
int iterations)
{
float4 best_min;
float4 best_max;
float4 center_pix = *(src_buf + src_width * y + x);
int i;
best_min = center_pix;
best_max = center_pix;
int angle_no = (src_width * y + x) * (iterations) *
samples + j * samples;
int radius_no = angle_no;
angle_no %= ANGLE_PRIME;
radius_no %= RADIUS_PRIME;
for(i=0; i<samples; i++)
{
int angle;
float rmag;
/* if we've sampled outside the valid image
area, we grab another sample instead, this
should potentially work better than mirroring
or extending the image */
angle = angle_no++;
rmag = radiuses[radius_no++] * radius;
if( angle_no >= ANGLE_PRIME)
angle_no = 0;
if( radius_no >= RADIUS_PRIME)
radius_no = 0;
int u = x + rmag * lut_cos[angle];
int v = y + rmag * lut_sin[angle];
if(u>=src_width || u <0 || v>=src_height || v<0)
{
//--i;
continue;
}
float4 pixel = *(src_buf + (src_width * v + u));
if(pixel.w<=0.0f)
{
//--i;
continue;
}
best_min = pixel < best_min ? pixel : best_min;
best_max = pixel > best_max ? pixel : best_max;
}
(*min).xyz = best_min.xyz;
(*max).xyz = best_max.xyz;
}
void compute_envelopes(const __global float4 *src_buf,
int src_width,
int src_height,
const __global float *radiuses,
const __global float *lut_cos,
const __global float *lut_sin,
int x,
int y,
int radius,
int samples,
int iterations,
float4 *min_envelope,
float4 *max_envelope)
{
float4 range_sum = 0;
float4 relative_brightness_sum = 0;
float4 pixel = *(src_buf + src_width * y + x);
int i;
for(i =0; i<iterations; i++)
{
float4 min,max;
float4 range, relative_brightness;
sample_min_max(src_buf, src_width, src_height,
radiuses, lut_cos, lut_sin, x, y,
radius,samples,&min,&max,i,iterations);
range = max - min;
relative_brightness = range <= 0.0f ?
0.5f : (pixel - min) / range;
relative_brightness_sum += relative_brightness;
range_sum += range;
}
float4 relative_brightness = relative_brightness_sum / (float4)(iterations);
float4 range = range_sum / (float4)(iterations);
if(max_envelope)
*max_envelope = pixel + (1.0f - relative_brightness) * range;
if(min_envelope)
*min_envelope = pixel - relative_brightness * range;
}
__kernel void c2g(const __global float4 *src_buf,
int src_width,
int src_height,
const __global float *radiuses,
const __global float *lut_cos,
const __global float *lut_sin,
__global float2 *dst_buf,
int radius,
int samples,
int iterations)
{
int gidx = get_global_id(0);
int gidy = get_global_id(1);
int x = gidx + radius;
int y = gidy + radius;
int src_offset = (src_width * y + x);
int dst_offset = gidx + get_global_size(0) * gidy;
float4 min,max;
compute_envelopes(src_buf, src_width, src_height,
radiuses, lut_cos, lut_sin, x, y,
radius, samples, iterations, &min, &max);
float4 pixel = *(src_buf + src_offset);
float nominator=0, denominator=0;
float4 t1 = (pixel - min) * (pixel - min);
float4 t2 = (pixel - max) * (pixel - max);
nominator = t1.x + t1.y + t1.z;
denominator = t2.x + t2.y + t2.z;
nominator = sqrt(nominator);
denominator = sqrt(denominator);
denominator+= nominator + denominator;
dst_buf[dst_offset].x = (denominator > 0.000f)
? (nominator / denominator) : 0.5f;
dst_buf[dst_offset].y = src_buf[src_offset].w;
}
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