15ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni/*
25ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni * Copyright (C) 2012 The Android Open Source Project
35ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni *
45ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni * Licensed under the Apache License, Version 2.0 (the "License");
55ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni * you may not use this file except in compliance with the License.
65ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni * You may obtain a copy of the License at
75ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni *
85ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni *      http://www.apache.org/licenses/LICENSE-2.0
95ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni *
105ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni * Unless required by applicable law or agreed to in writing, software
115ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni * distributed under the License is distributed on an "AS IS" BASIS,
125ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
135ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni * See the License for the specific language governing permissions and
145ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni * limitations under the License.
155ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni */
165ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni
175ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Nistatic float2 neg_center, axis_scale, inv_dimensions;
185ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Nistatic float sloped_neg_range, sloped_inv_max_dist, shade, opp_shade;
195ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni
205ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Nivoid init_vignette(uint32_t dim_x, uint32_t dim_y, float center_x, float center_y,
215ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni        float desired_scale, float desired_shade, float desired_slope) {
225ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni
235ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni    neg_center.x = -center_x;
245ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni    neg_center.y = -center_y;
255ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni    inv_dimensions.x = 1.f / (float)dim_x;
265ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni    inv_dimensions.y = 1.f / (float)dim_y;
275ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni
285ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni    axis_scale = (float2)1.f;
295ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni    if (dim_x > dim_y)
305ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni        axis_scale.y = (float)dim_y / (float)dim_x;
315ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni    else
325ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni        axis_scale.x = (float)dim_x / (float)dim_y;
335ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni
345ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni    const float max_dist = 0.5f * length(axis_scale);
355ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni    sloped_inv_max_dist = desired_slope * 1.f/max_dist;
365ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni
375ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni    // Range needs to be between 1.3 to 0.6. When scale is zero then range is
385ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni    // 1.3 which means no vignette at all because the luminousity difference is
395ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni    // less than 1/256.  Expect input scale to be between 0.0 and 1.0.
405ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni    const float neg_range = 0.7f*sqrt(desired_scale) - 1.3f;
415ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni    sloped_neg_range = exp(neg_range * desired_slope);
425ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni
435ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni    shade = desired_shade;
445ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni    opp_shade = 1.f - desired_shade;
455ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni}
465ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni
475ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Nifloat4 __attribute__((kernel)) vignette(float4 in, uint32_t x, uint32_t y) {
485ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni    // Convert x and y to floating point coordinates with center as origin
495ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni    const float2 inCoord = {(float)x, (float)y};
505ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni    const float2 coord = mad(inCoord, inv_dimensions, neg_center);
515ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni    const float sloped_dist_ratio = fast_length(axis_scale * coord)  * sloped_inv_max_dist;
525ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni    const float lumen = opp_shade + shade * half_recip(1.f + sloped_neg_range * native_exp(sloped_dist_ratio));
535ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni    float4 fout;
545ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni    fout.rgb = in.rgb * lumen;
555ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni    fout.w = in.w;
565ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni    return fout;
575ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni}
585ab5155f7e0e0904f8c11cd0dbdbf7832e3ac948Yang Ni
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