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/*

 * 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 0xxx, then the compression type is "basic",

 *             values greater than 1001 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" 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", the following data stream looks like

 * this:

 *

 *   1..3 bytes:  data size (N) in compact representation;

 *   N bytes:     JPEG 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" or "jpeg".

 *

 *-- 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_MAX_SUBENCODING       0x09

/* 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 */