--- /dev/null
+/*
+ * 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 */
Code Review / kvmfornfv.git / blobdiff