1 // Copyright 2014 Google Inc. All Rights Reserved.
2 //
3 // Use of this source code is governed by a BSD-style license
4 // that can be found in the COPYING file in the root of the source
5 // tree. An additional intellectual property rights grant can be found
6 // in the file PATENTS. All contributing project authors may
7 // be found in the AUTHORS file in the root of the source tree.
8 // -----------------------------------------------------------------------------
9 //
10 // WebPPicture tools: alpha handling, etc.
11 //
12 // Author: Skal (pascal.massimino@gmail.com)
13 
14 #include "./vp8enci.h"
15 #include "../dsp/yuv.h"
16 
MakeARGB32(int r,int g,int b)17 static WEBP_INLINE uint32_t MakeARGB32(int r, int g, int b) {
18   return (0xff000000u | (r << 16) | (g << 8) | b);
19 }
20 
21 //------------------------------------------------------------------------------
22 // Helper: clean up fully transparent area to help compressibility.
23 
24 #define SIZE 8
25 #define SIZE2 (SIZE / 2)
is_transparent_area(const uint8_t * ptr,int stride,int size)26 static int is_transparent_area(const uint8_t* ptr, int stride, int size) {
27   int y, x;
28   for (y = 0; y < size; ++y) {
29     for (x = 0; x < size; ++x) {
30       if (ptr[x]) {
31         return 0;
32       }
33     }
34     ptr += stride;
35   }
36   return 1;
37 }
38 
is_transparent_argb_area(const uint32_t * ptr,int stride,int size)39 static int is_transparent_argb_area(const uint32_t* ptr, int stride, int size) {
40   int y, x;
41   for (y = 0; y < size; ++y) {
42     for (x = 0; x < size; ++x) {
43       if (ptr[x] & 0xff000000u) {
44         return 0;
45       }
46     }
47     ptr += stride;
48   }
49   return 1;
50 }
51 
flatten(uint8_t * ptr,int v,int stride,int size)52 static void flatten(uint8_t* ptr, int v, int stride, int size) {
53   int y;
54   for (y = 0; y < size; ++y) {
55     memset(ptr, v, size);
56     ptr += stride;
57   }
58 }
59 
flatten_argb(uint32_t * ptr,uint32_t v,int stride,int size)60 static void flatten_argb(uint32_t* ptr, uint32_t v, int stride, int size) {
61   int x, y;
62   for (y = 0; y < size; ++y) {
63     for (x = 0; x < size; ++x) ptr[x] = v;
64     ptr += stride;
65   }
66 }
67 
WebPCleanupTransparentArea(WebPPicture * pic)68 void WebPCleanupTransparentArea(WebPPicture* pic) {
69   int x, y, w, h;
70   if (pic == NULL) return;
71   w = pic->width / SIZE;
72   h = pic->height / SIZE;
73 
74   // note: we ignore the left-overs on right/bottom
75   if (pic->use_argb) {
76     uint32_t argb_value = 0;
77     for (y = 0; y < h; ++y) {
78       int need_reset = 1;
79       for (x = 0; x < w; ++x) {
80         const int off = (y * pic->argb_stride + x) * SIZE;
81         if (is_transparent_argb_area(pic->argb + off, pic->argb_stride, SIZE)) {
82           if (need_reset) {
83             argb_value = pic->argb[off];
84             need_reset = 0;
85           }
86           flatten_argb(pic->argb + off, argb_value, pic->argb_stride, SIZE);
87         } else {
88           need_reset = 1;
89         }
90       }
91     }
92   } else {
93     const uint8_t* const a_ptr = pic->a;
94     int values[3] = { 0 };
95     if (a_ptr == NULL) return;    // nothing to do
96     for (y = 0; y < h; ++y) {
97       int need_reset = 1;
98       for (x = 0; x < w; ++x) {
99         const int off_a = (y * pic->a_stride + x) * SIZE;
100         const int off_y = (y * pic->y_stride + x) * SIZE;
101         const int off_uv = (y * pic->uv_stride + x) * SIZE2;
102         if (is_transparent_area(a_ptr + off_a, pic->a_stride, SIZE)) {
103           if (need_reset) {
104             values[0] = pic->y[off_y];
105             values[1] = pic->u[off_uv];
106             values[2] = pic->v[off_uv];
107             need_reset = 0;
108           }
109           flatten(pic->y + off_y, values[0], pic->y_stride, SIZE);
110           flatten(pic->u + off_uv, values[1], pic->uv_stride, SIZE2);
111           flatten(pic->v + off_uv, values[2], pic->uv_stride, SIZE2);
112         } else {
113           need_reset = 1;
114         }
115       }
116     }
117   }
118 }
119 
120 #undef SIZE
121 #undef SIZE2
122 
123 //------------------------------------------------------------------------------
124 // Blend color and remove transparency info
125 
126 #define BLEND(V0, V1, ALPHA) \
127     ((((V0) * (255 - (ALPHA)) + (V1) * (ALPHA)) * 0x101) >> 16)
128 #define BLEND_10BIT(V0, V1, ALPHA) \
129     ((((V0) * (1020 - (ALPHA)) + (V1) * (ALPHA)) * 0x101) >> 18)
130 
WebPBlendAlpha(WebPPicture * pic,uint32_t background_rgb)131 void WebPBlendAlpha(WebPPicture* pic, uint32_t background_rgb) {
132   const int red = (background_rgb >> 16) & 0xff;
133   const int green = (background_rgb >> 8) & 0xff;
134   const int blue = (background_rgb >> 0) & 0xff;
135   int x, y;
136   if (pic == NULL) return;
137   if (!pic->use_argb) {
138     const int uv_width = (pic->width >> 1);  // omit last pixel during u/v loop
139     const int Y0 = VP8RGBToY(red, green, blue, YUV_HALF);
140     // VP8RGBToU/V expects the u/v values summed over four pixels
141     const int U0 = VP8RGBToU(4 * red, 4 * green, 4 * blue, 4 * YUV_HALF);
142     const int V0 = VP8RGBToV(4 * red, 4 * green, 4 * blue, 4 * YUV_HALF);
143     const int has_alpha = pic->colorspace & WEBP_CSP_ALPHA_BIT;
144     if (!has_alpha || pic->a == NULL) return;    // nothing to do
145     for (y = 0; y < pic->height; ++y) {
146       // Luma blending
147       uint8_t* const y_ptr = pic->y + y * pic->y_stride;
148       uint8_t* const a_ptr = pic->a + y * pic->a_stride;
149       for (x = 0; x < pic->width; ++x) {
150         const int alpha = a_ptr[x];
151         if (alpha < 0xff) {
152           y_ptr[x] = BLEND(Y0, y_ptr[x], a_ptr[x]);
153         }
154       }
155       // Chroma blending every even line
156       if ((y & 1) == 0) {
157         uint8_t* const u = pic->u + (y >> 1) * pic->uv_stride;
158         uint8_t* const v = pic->v + (y >> 1) * pic->uv_stride;
159         uint8_t* const a_ptr2 =
160             (y + 1 == pic->height) ? a_ptr : a_ptr + pic->a_stride;
161         for (x = 0; x < uv_width; ++x) {
162           // Average four alpha values into a single blending weight.
163           // TODO(skal): might lead to visible contouring. Can we do better?
164           const int alpha =
165               a_ptr[2 * x + 0] + a_ptr[2 * x + 1] +
166               a_ptr2[2 * x + 0] + a_ptr2[2 * x + 1];
167           u[x] = BLEND_10BIT(U0, u[x], alpha);
168           v[x] = BLEND_10BIT(V0, v[x], alpha);
169         }
170         if (pic->width & 1) {   // rightmost pixel
171           const int alpha = 2 * (a_ptr[2 * x + 0] + a_ptr2[2 * x + 0]);
172           u[x] = BLEND_10BIT(U0, u[x], alpha);
173           v[x] = BLEND_10BIT(V0, v[x], alpha);
174         }
175       }
176       memset(a_ptr, 0xff, pic->width);
177     }
178   } else {
179     uint32_t* argb = pic->argb;
180     const uint32_t background = MakeARGB32(red, green, blue);
181     for (y = 0; y < pic->height; ++y) {
182       for (x = 0; x < pic->width; ++x) {
183         const int alpha = (argb[x] >> 24) & 0xff;
184         if (alpha != 0xff) {
185           if (alpha > 0) {
186             int r = (argb[x] >> 16) & 0xff;
187             int g = (argb[x] >>  8) & 0xff;
188             int b = (argb[x] >>  0) & 0xff;
189             r = BLEND(red, r, alpha);
190             g = BLEND(green, g, alpha);
191             b = BLEND(blue, b, alpha);
192             argb[x] = MakeARGB32(r, g, b);
193           } else {
194             argb[x] = background;
195           }
196         }
197       }
198       argb += pic->argb_stride;
199     }
200   }
201 }
202 
203 #undef BLEND
204 #undef BLEND_10BIT
205 
206 //------------------------------------------------------------------------------
207