1245f7b51SCorentin Chary /* 2245f7b51SCorentin Chary * QEMU VNC display driver: tight encoding 3245f7b51SCorentin Chary * 4245f7b51SCorentin Chary * From libvncserver/rfb/rfbproto.h 5245f7b51SCorentin Chary * Copyright (C) 2005 Rohit Kumar, Johannes E. Schindelin 6245f7b51SCorentin Chary * Copyright (C) 2000-2002 Constantin Kaplinsky. All Rights Reserved. 7245f7b51SCorentin Chary * Copyright (C) 2000 Tridia Corporation. All Rights Reserved. 8245f7b51SCorentin Chary * Copyright (C) 1999 AT&T Laboratories Cambridge. All Rights Reserved. 9245f7b51SCorentin Chary * 10245f7b51SCorentin Chary * 11245f7b51SCorentin Chary * Permission is hereby granted, free of charge, to any person obtaining a copy 12245f7b51SCorentin Chary * of this software and associated documentation files (the "Software"), to deal 13245f7b51SCorentin Chary * in the Software without restriction, including without limitation the rights 14245f7b51SCorentin Chary * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 15245f7b51SCorentin Chary * copies of the Software, and to permit persons to whom the Software is 16245f7b51SCorentin Chary * furnished to do so, subject to the following conditions: 17245f7b51SCorentin Chary * 18245f7b51SCorentin Chary * The above copyright notice and this permission notice shall be included in 19245f7b51SCorentin Chary * all copies or substantial portions of the Software. 20245f7b51SCorentin Chary * 21245f7b51SCorentin Chary * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 22245f7b51SCorentin Chary * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 23245f7b51SCorentin Chary * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL 24245f7b51SCorentin Chary * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 25245f7b51SCorentin Chary * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 26245f7b51SCorentin Chary * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN 27245f7b51SCorentin Chary * THE SOFTWARE. 28245f7b51SCorentin Chary */ 29245f7b51SCorentin Chary 30*121d0712SMarkus Armbruster #ifndef VNC_ENC_TIGHT_H 31*121d0712SMarkus Armbruster #define VNC_ENC_TIGHT_H 32245f7b51SCorentin Chary 33245f7b51SCorentin Chary /*- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 34245f7b51SCorentin Chary * Tight Encoding. 35245f7b51SCorentin Chary * 36245f7b51SCorentin Chary *-- The first byte of each Tight-encoded rectangle is a "compression control 37245f7b51SCorentin Chary * byte". Its format is as follows (bit 0 is the least significant one): 38245f7b51SCorentin Chary * 39245f7b51SCorentin Chary * bit 0: if 1, then compression stream 0 should be reset; 40245f7b51SCorentin Chary * bit 1: if 1, then compression stream 1 should be reset; 41245f7b51SCorentin Chary * bit 2: if 1, then compression stream 2 should be reset; 42245f7b51SCorentin Chary * bit 3: if 1, then compression stream 3 should be reset; 43245f7b51SCorentin Chary * bits 7-4: if 1000 (0x08), then the compression type is "fill", 44245f7b51SCorentin Chary * if 1001 (0x09), then the compression type is "jpeg", 45efe556adSCorentin Chary * if 1010 (0x0A), then the compression type is "png", 46245f7b51SCorentin Chary * if 0xxx, then the compression type is "basic", 47efe556adSCorentin Chary * values greater than 1010 are not valid. 48245f7b51SCorentin Chary * 49245f7b51SCorentin Chary * If the compression type is "basic", then bits 6..4 of the 50245f7b51SCorentin Chary * compression control byte (those xxx in 0xxx) specify the following: 51245f7b51SCorentin Chary * 52245f7b51SCorentin Chary * bits 5-4: decimal representation is the index of a particular zlib 53245f7b51SCorentin Chary * stream which should be used for decompressing the data; 54245f7b51SCorentin Chary * bit 6: if 1, then a "filter id" byte is following this byte. 55245f7b51SCorentin Chary * 56245f7b51SCorentin Chary *-- The data that follows after the compression control byte described 57efe556adSCorentin Chary * above depends on the compression type ("fill", "jpeg", "png" or "basic"). 58245f7b51SCorentin Chary * 59245f7b51SCorentin Chary *-- If the compression type is "fill", then the only pixel value follows, in 60245f7b51SCorentin Chary * client pixel format (see NOTE 1). This value applies to all pixels of the 61245f7b51SCorentin Chary * rectangle. 62245f7b51SCorentin Chary * 63efe556adSCorentin Chary *-- If the compression type is "jpeg" or "png", the following data stream 64efe556adSCorentin Chary * looks like this: 65245f7b51SCorentin Chary * 66245f7b51SCorentin Chary * 1..3 bytes: data size (N) in compact representation; 67efe556adSCorentin Chary * N bytes: JPEG or PNG image. 68245f7b51SCorentin Chary * 69245f7b51SCorentin Chary * Data size is compactly represented in one, two or three bytes, according 70245f7b51SCorentin Chary * to the following scheme: 71245f7b51SCorentin Chary * 72245f7b51SCorentin Chary * 0xxxxxxx (for values 0..127) 73245f7b51SCorentin Chary * 1xxxxxxx 0yyyyyyy (for values 128..16383) 74245f7b51SCorentin Chary * 1xxxxxxx 1yyyyyyy zzzzzzzz (for values 16384..4194303) 75245f7b51SCorentin Chary * 76245f7b51SCorentin Chary * Here each character denotes one bit, xxxxxxx are the least significant 7 77245f7b51SCorentin Chary * bits of the value (bits 0-6), yyyyyyy are bits 7-13, and zzzzzzzz are the 78245f7b51SCorentin Chary * most significant 8 bits (bits 14-21). For example, decimal value 10000 79245f7b51SCorentin Chary * should be represented as two bytes: binary 10010000 01001110, or 80245f7b51SCorentin Chary * hexadecimal 90 4E. 81245f7b51SCorentin Chary * 82245f7b51SCorentin Chary *-- If the compression type is "basic" and bit 6 of the compression control 83245f7b51SCorentin Chary * byte was set to 1, then the next (second) byte specifies "filter id" which 84245f7b51SCorentin Chary * tells the decoder what filter type was used by the encoder to pre-process 85245f7b51SCorentin Chary * pixel data before the compression. The "filter id" byte can be one of the 86245f7b51SCorentin Chary * following: 87245f7b51SCorentin Chary * 88245f7b51SCorentin Chary * 0: no filter ("copy" filter); 89245f7b51SCorentin Chary * 1: "palette" filter; 90245f7b51SCorentin Chary * 2: "gradient" filter. 91245f7b51SCorentin Chary * 92245f7b51SCorentin Chary *-- If bit 6 of the compression control byte is set to 0 (no "filter id" 93245f7b51SCorentin Chary * byte), or if the filter id is 0, then raw pixel values in the client 94245f7b51SCorentin Chary * format (see NOTE 1) will be compressed. See below details on the 95245f7b51SCorentin Chary * compression. 96245f7b51SCorentin Chary * 97245f7b51SCorentin Chary *-- The "gradient" filter pre-processes pixel data with a simple algorithm 98245f7b51SCorentin Chary * which converts each color component to a difference between a "predicted" 99245f7b51SCorentin Chary * intensity and the actual intensity. Such a technique does not affect 100245f7b51SCorentin Chary * uncompressed data size, but helps to compress photo-like images better. 101245f7b51SCorentin Chary * Pseudo-code for converting intensities to differences is the following: 102245f7b51SCorentin Chary * 103245f7b51SCorentin Chary * P[i,j] := V[i-1,j] + V[i,j-1] - V[i-1,j-1]; 104245f7b51SCorentin Chary * if (P[i,j] < 0) then P[i,j] := 0; 105245f7b51SCorentin Chary * if (P[i,j] > MAX) then P[i,j] := MAX; 106245f7b51SCorentin Chary * D[i,j] := V[i,j] - P[i,j]; 107245f7b51SCorentin Chary * 108245f7b51SCorentin Chary * Here V[i,j] is the intensity of a color component for a pixel at 109245f7b51SCorentin Chary * coordinates (i,j). MAX is the maximum value of intensity for a color 110245f7b51SCorentin Chary * component. 111245f7b51SCorentin Chary * 112245f7b51SCorentin Chary *-- The "palette" filter converts true-color pixel data to indexed colors 113245f7b51SCorentin Chary * and a palette which can consist of 2..256 colors. If the number of colors 114245f7b51SCorentin Chary * is 2, then each pixel is encoded in 1 bit, otherwise 8 bits is used to 115245f7b51SCorentin Chary * encode one pixel. 1-bit encoding is performed such way that the most 116245f7b51SCorentin Chary * significant bits correspond to the leftmost pixels, and each raw of pixels 117245f7b51SCorentin Chary * is aligned to the byte boundary. When "palette" filter is used, the 118245f7b51SCorentin Chary * palette is sent before the pixel data. The palette begins with an unsigned 119245f7b51SCorentin Chary * byte which value is the number of colors in the palette minus 1 (i.e. 1 120245f7b51SCorentin Chary * means 2 colors, 255 means 256 colors in the palette). Then follows the 121245f7b51SCorentin Chary * palette itself which consist of pixel values in client pixel format (see 122245f7b51SCorentin Chary * NOTE 1). 123245f7b51SCorentin Chary * 124245f7b51SCorentin Chary *-- The pixel data is compressed using the zlib library. But if the data 125245f7b51SCorentin Chary * size after applying the filter but before the compression is less then 12, 126245f7b51SCorentin Chary * then the data is sent as is, uncompressed. Four separate zlib streams 127245f7b51SCorentin Chary * (0..3) can be used and the decoder should read the actual stream id from 128245f7b51SCorentin Chary * the compression control byte (see NOTE 2). 129245f7b51SCorentin Chary * 130245f7b51SCorentin Chary * If the compression is not used, then the pixel data is sent as is, 131245f7b51SCorentin Chary * otherwise the data stream looks like this: 132245f7b51SCorentin Chary * 133245f7b51SCorentin Chary * 1..3 bytes: data size (N) in compact representation; 134245f7b51SCorentin Chary * N bytes: zlib-compressed data. 135245f7b51SCorentin Chary * 136245f7b51SCorentin Chary * Data size is compactly represented in one, two or three bytes, just like 137245f7b51SCorentin Chary * in the "jpeg" compression method (see above). 138245f7b51SCorentin Chary * 139245f7b51SCorentin Chary *-- NOTE 1. If the color depth is 24, and all three color components are 140245f7b51SCorentin Chary * 8-bit wide, then one pixel in Tight encoding is always represented by 141245f7b51SCorentin Chary * three bytes, where the first byte is red component, the second byte is 142245f7b51SCorentin Chary * green component, and the third byte is blue component of the pixel color 143245f7b51SCorentin Chary * value. This applies to colors in palettes as well. 144245f7b51SCorentin Chary * 145245f7b51SCorentin Chary *-- NOTE 2. The decoder must reset compression streams' states before 146245f7b51SCorentin Chary * decoding the rectangle, if some of bits 0,1,2,3 in the compression control 147245f7b51SCorentin Chary * byte are set to 1. Note that the decoder must reset zlib streams even if 148efe556adSCorentin Chary * the compression type is "fill", "jpeg" or "png". 149245f7b51SCorentin Chary * 150245f7b51SCorentin Chary *-- NOTE 3. The "gradient" filter and "jpeg" compression may be used only 151245f7b51SCorentin Chary * when bits-per-pixel value is either 16 or 32, not 8. 152245f7b51SCorentin Chary * 153245f7b51SCorentin Chary *-- NOTE 4. The width of any Tight-encoded rectangle cannot exceed 2048 154245f7b51SCorentin Chary * pixels. If a rectangle is wider, it must be split into several rectangles 155245f7b51SCorentin Chary * and each one should be encoded separately. 156245f7b51SCorentin Chary * 157245f7b51SCorentin Chary */ 158245f7b51SCorentin Chary 159245f7b51SCorentin Chary #define VNC_TIGHT_EXPLICIT_FILTER 0x04 160245f7b51SCorentin Chary #define VNC_TIGHT_FILL 0x08 161245f7b51SCorentin Chary #define VNC_TIGHT_JPEG 0x09 162efe556adSCorentin Chary #define VNC_TIGHT_PNG 0x0A 163efe556adSCorentin Chary #define VNC_TIGHT_MAX_SUBENCODING 0x0A 164245f7b51SCorentin Chary 165245f7b51SCorentin Chary /* Filters to improve compression efficiency */ 166245f7b51SCorentin Chary #define VNC_TIGHT_FILTER_COPY 0x00 167245f7b51SCorentin Chary #define VNC_TIGHT_FILTER_PALETTE 0x01 168245f7b51SCorentin Chary #define VNC_TIGHT_FILTER_GRADIENT 0x02 169245f7b51SCorentin Chary 170245f7b51SCorentin Chary /* Note: The following constant should not be changed. */ 171245f7b51SCorentin Chary #define VNC_TIGHT_MIN_TO_COMPRESS 12 172245f7b51SCorentin Chary 173245f7b51SCorentin Chary /* The parameters below may be adjusted. */ 174245f7b51SCorentin Chary #define VNC_TIGHT_MIN_SPLIT_RECT_SIZE 4096 175245f7b51SCorentin Chary #define VNC_TIGHT_MIN_SOLID_SUBRECT_SIZE 2048 176245f7b51SCorentin Chary #define VNC_TIGHT_MAX_SPLIT_TILE_SIZE 16 177245f7b51SCorentin Chary 178245f7b51SCorentin Chary #define VNC_TIGHT_JPEG_MIN_RECT_SIZE 4096 179245f7b51SCorentin Chary #define VNC_TIGHT_DETECT_SUBROW_WIDTH 7 180245f7b51SCorentin Chary #define VNC_TIGHT_DETECT_MIN_WIDTH 8 181245f7b51SCorentin Chary #define VNC_TIGHT_DETECT_MIN_HEIGHT 8 182245f7b51SCorentin Chary 183*121d0712SMarkus Armbruster #endif /* VNC_ENC_TIGHT_H */ 184