| /* |
| * Copyright (C) 2012 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. |
| */ |
| |
| rs_allocation in_alloc; |
| rs_sampler sampler; |
| |
| static float2 center, neg_center, inv_dimensions, axis_scale; |
| static float alpha, radius2, factor; |
| |
| void init_filter(uint32_t dim_x, uint32_t dim_y, float center_x, float center_y, float k) { |
| center.x = center_x; |
| center.y = center_y; |
| neg_center = -center; |
| inv_dimensions.x = 1.f / (float)dim_x; |
| inv_dimensions.y = 1.f / (float)dim_y; |
| alpha = k * 2.0f + 0.75f; |
| |
| axis_scale = (float2)1.f; |
| if (dim_x > dim_y) |
| axis_scale.y = (float)dim_y / (float)dim_x; |
| else |
| axis_scale.x = (float)dim_x / (float)dim_y; |
| |
| const float bound2 = 0.25f * (axis_scale.x*axis_scale.x + axis_scale.y*axis_scale.y); |
| const float bound = sqrt(bound2); |
| const float radius = 1.15f * bound; |
| radius2 = radius*radius; |
| const float max_radian = M_PI_2 - atan(alpha / bound * sqrt(radius2 - bound2)); |
| factor = bound / max_radian; |
| } |
| |
| uchar4 __attribute__((kernel)) root(uint32_t x, uint32_t y) { |
| // Convert x and y to floating point coordinates with center as origin |
| const float2 inCoord = {(float)x, (float)y}; |
| const float2 coord = mad(inCoord, inv_dimensions, neg_center); |
| const float2 scaledCoord = axis_scale * coord; |
| const float dist2 = scaledCoord.x*scaledCoord.x + scaledCoord.y*scaledCoord.y; |
| const float inv_dist = half_rsqrt(dist2); |
| const float radian = M_PI_2 - atan((alpha * half_sqrt(radius2 - dist2)) * inv_dist); |
| const float scalar = radian * factor * inv_dist; |
| const float2 new_coord = mad(coord, scalar, center); |
| const float4 fout = rsSample(in_alloc, sampler, new_coord); |
| return rsPackColorTo8888(fout); |
| } |
| |