vnc-encoding-tight.h - qemu - Git at Google

 /*
  * 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

 #endif /* VNC_ENCODING_TIGHT_H */
	/*
	* 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

	#endif /* VNC_ENCODING_TIGHT_H */