| /* |
| * QEMU VNC display driver: tight encoding |
| * |
| * From libvncserver/rfb/rfbproto.h |
| * Copyright (C) 2005 Rohit Kumar, Johannes E. Schindelin |
| * Copyright (C) 2000-2002 Constantin Kaplinsky. All Rights Reserved. |
| * Copyright (C) 2000 Tridia Corporation. All Rights Reserved. |
| * Copyright (C) 1999 AT&T Laboratories Cambridge. All Rights Reserved. |
| * |
| * |
| * Permission is hereby granted, free of charge, to any person obtaining a copy |
| * of this software and associated documentation files (the "Software"), to deal |
| * in the Software without restriction, including without limitation the rights |
| * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell |
| * copies of the Software, and to permit persons to whom the Software is |
| * furnished to do so, subject to the following conditions: |
| * |
| * The above copyright notice and this permission notice shall be included in |
| * all copies or substantial portions of the Software. |
| * |
| * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
| * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
| * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL |
| * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
| * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, |
| * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN |
| * THE SOFTWARE. |
| */ |
| |
| #ifndef VNC_ENCODING_TIGHT_H |
| #define VNC_ENCODING_TIGHT_H |
| |
| /*- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - |
| * Tight Encoding. |
| * |
| *-- The first byte of each Tight-encoded rectangle is a "compression control |
| * byte". Its format is as follows (bit 0 is the least significant one): |
| * |
| * bit 0: if 1, then compression stream 0 should be reset; |
| * bit 1: if 1, then compression stream 1 should be reset; |
| * bit 2: if 1, then compression stream 2 should be reset; |
| * bit 3: if 1, then compression stream 3 should be reset; |
| * bits 7-4: if 1000 (0x08), then the compression type is "fill", |
| * if 1001 (0x09), then the compression type is "jpeg", |
| * if 1010 (0x0A), then the compression type is "png", |
| * if 0xxx, then the compression type is "basic", |
| * values greater than 1010 are not valid. |
| * |
| * If the compression type is "basic", then bits 6..4 of the |
| * compression control byte (those xxx in 0xxx) specify the following: |
| * |
| * bits 5-4: decimal representation is the index of a particular zlib |
| * stream which should be used for decompressing the data; |
| * bit 6: if 1, then a "filter id" byte is following this byte. |
| * |
| *-- The data that follows after the compression control byte described |
| * above depends on the compression type ("fill", "jpeg", "png" or "basic"). |
| * |
| *-- If the compression type is "fill", then the only pixel value follows, in |
| * client pixel format (see NOTE 1). This value applies to all pixels of the |
| * rectangle. |
| * |
| *-- If the compression type is "jpeg" or "png", the following data stream |
| * looks like this: |
| * |
| * 1..3 bytes: data size (N) in compact representation; |
| * N bytes: JPEG or PNG image. |
| * |
| * Data size is compactly represented in one, two or three bytes, according |
| * to the following scheme: |
| * |
| * 0xxxxxxx (for values 0..127) |
| * 1xxxxxxx 0yyyyyyy (for values 128..16383) |
| * 1xxxxxxx 1yyyyyyy zzzzzzzz (for values 16384..4194303) |
| * |
| * Here each character denotes one bit, xxxxxxx are the least significant 7 |
| * bits of the value (bits 0-6), yyyyyyy are bits 7-13, and zzzzzzzz are the |
| * most significant 8 bits (bits 14-21). For example, decimal value 10000 |
| * should be represented as two bytes: binary 10010000 01001110, or |
| * hexadecimal 90 4E. |
| * |
| *-- If the compression type is "basic" and bit 6 of the compression control |
| * byte was set to 1, then the next (second) byte specifies "filter id" which |
| * tells the decoder what filter type was used by the encoder to pre-process |
| * pixel data before the compression. The "filter id" byte can be one of the |
| * following: |
| * |
| * 0: no filter ("copy" filter); |
| * 1: "palette" filter; |
| * 2: "gradient" filter. |
| * |
| *-- If bit 6 of the compression control byte is set to 0 (no "filter id" |
| * byte), or if the filter id is 0, then raw pixel values in the client |
| * format (see NOTE 1) will be compressed. See below details on the |
| * compression. |
| * |
| *-- The "gradient" filter pre-processes pixel data with a simple algorithm |
| * which converts each color component to a difference between a "predicted" |
| * intensity and the actual intensity. Such a technique does not affect |
| * uncompressed data size, but helps to compress photo-like images better. |
| * Pseudo-code for converting intensities to differences is the following: |
| * |
| * P[i,j] := V[i-1,j] + V[i,j-1] - V[i-1,j-1]; |
| * if (P[i,j] < 0) then P[i,j] := 0; |
| * if (P[i,j] > MAX) then P[i,j] := MAX; |
| * D[i,j] := V[i,j] - P[i,j]; |
| * |
| * Here V[i,j] is the intensity of a color component for a pixel at |
| * coordinates (i,j). MAX is the maximum value of intensity for a color |
| * component. |
| * |
| *-- The "palette" filter converts true-color pixel data to indexed colors |
| * and a palette which can consist of 2..256 colors. If the number of colors |
| * is 2, then each pixel is encoded in 1 bit, otherwise 8 bits is used to |
| * encode one pixel. 1-bit encoding is performed such way that the most |
| * significant bits correspond to the leftmost pixels, and each raw of pixels |
| * is aligned to the byte boundary. When "palette" filter is used, the |
| * palette is sent before the pixel data. The palette begins with an unsigned |
| * byte which value is the number of colors in the palette minus 1 (i.e. 1 |
| * means 2 colors, 255 means 256 colors in the palette). Then follows the |
| * palette itself which consist of pixel values in client pixel format (see |
| * NOTE 1). |
| * |
| *-- The pixel data is compressed using the zlib library. But if the data |
| * size after applying the filter but before the compression is less then 12, |
| * then the data is sent as is, uncompressed. Four separate zlib streams |
| * (0..3) can be used and the decoder should read the actual stream id from |
| * the compression control byte (see NOTE 2). |
| * |
| * If the compression is not used, then the pixel data is sent as is, |
| * otherwise the data stream looks like this: |
| * |
| * 1..3 bytes: data size (N) in compact representation; |
| * N bytes: zlib-compressed data. |
| * |
| * Data size is compactly represented in one, two or three bytes, just like |
| * in the "jpeg" compression method (see above). |
| * |
| *-- NOTE 1. If the color depth is 24, and all three color components are |
| * 8-bit wide, then one pixel in Tight encoding is always represented by |
| * three bytes, where the first byte is red component, the second byte is |
| * green component, and the third byte is blue component of the pixel color |
| * value. This applies to colors in palettes as well. |
| * |
| *-- NOTE 2. The decoder must reset compression streams' states before |
| * decoding the rectangle, if some of bits 0,1,2,3 in the compression control |
| * byte are set to 1. Note that the decoder must reset zlib streams even if |
| * the compression type is "fill", "jpeg" or "png". |
| * |
| *-- NOTE 3. The "gradient" filter and "jpeg" compression may be used only |
| * when bits-per-pixel value is either 16 or 32, not 8. |
| * |
| *-- NOTE 4. The width of any Tight-encoded rectangle cannot exceed 2048 |
| * pixels. If a rectangle is wider, it must be split into several rectangles |
| * and each one should be encoded separately. |
| * |
| */ |
| |
| #define VNC_TIGHT_EXPLICIT_FILTER 0x04 |
| #define VNC_TIGHT_FILL 0x08 |
| #define VNC_TIGHT_JPEG 0x09 |
| #define VNC_TIGHT_PNG 0x0A |
| #define VNC_TIGHT_MAX_SUBENCODING 0x0A |
| |
| /* Filters to improve compression efficiency */ |
| #define VNC_TIGHT_FILTER_COPY 0x00 |
| #define VNC_TIGHT_FILTER_PALETTE 0x01 |
| #define VNC_TIGHT_FILTER_GRADIENT 0x02 |
| |
| /* Note: The following constant should not be changed. */ |
| #define VNC_TIGHT_MIN_TO_COMPRESS 12 |
| |
| /* The parameters below may be adjusted. */ |
| #define VNC_TIGHT_MIN_SPLIT_RECT_SIZE 4096 |
| #define VNC_TIGHT_MIN_SOLID_SUBRECT_SIZE 2048 |
| #define VNC_TIGHT_MAX_SPLIT_TILE_SIZE 16 |
| |
| #define VNC_TIGHT_JPEG_MIN_RECT_SIZE 4096 |
| #define VNC_TIGHT_DETECT_SUBROW_WIDTH 7 |
| #define VNC_TIGHT_DETECT_MIN_WIDTH 8 |
| #define VNC_TIGHT_DETECT_MIN_HEIGHT 8 |
| |
| #endif /* VNC_ENCODING_TIGHT_H */ |
