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Add: SpriteEncoder source code, description, and a simple decoder.
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‎SpriteEncoder/32bpp_pixformat.txt‎

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Copyright (c) 2013 Albert "Alberth" Hofkamp
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Permission is hereby granted, free of charge, to any person obtaining a copy of
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this software and associated documentation files (the "Software"), to deal in
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the Software without restriction, including without limitation the rights to
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use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
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of the Software, and to permit persons to whom the Software is furnished to do
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so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in all
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copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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SOFTWARE.
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Pixel format of 32bpp images.
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The pixel format supports image sizes of up to 65534x65534 pixels, allows
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transparency, and up to 256 recolour layers.
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The file starts with
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- 4 bytes header "CTHG"
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- 2 bytes version number (low endian), currently version 2
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- zero or more sprites.
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A sprite has
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- 4 bytes length of this sprite (low endian), length excludes these 4 bytes.
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- 2 bytes sprite number (low endian).
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- 2 bytes width of the sprite (low endian).
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- 2 bytes height of the sprite (low endian).
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- (width * height) pixel data as a continuous stream.
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The pixel data starts at the top-left pixel, and runs horizontally (and
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continues at the left of the next line when reaching the end). This continues
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until the last pixel at the bottom-right has been written.
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Sequences of pixels with the same characteristics are taken together in blocks
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of up to 64 pixels long, and encoded. There are four types of blocks:
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1. Fixed fully opaque 32bpp pixels (all the coloured pixels that are always the
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same).
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2. Fixed partially transparent 32bpp pixels (glow effects, or 50% transparency).
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3. Fixed fully transparent pixels (empty space around the displayed shape to
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make it a rectangular image).
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4. Recolour layer (pixels that are retrieved from an RGB table with 256 entries
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that acts like a palette). The data stored in the sprite is just the index
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to use for each pixel. Opacity is the same for the entire block.
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Typically there are tables with ranges of colours, and the sprite contains
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the intensity as the index.
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Below is the encoding for each type of pixel block:
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1. Fixed fully opaque 32bpp pixels (RGB).
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- 1 byte length (values 0-63)
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- N x 3 byte pixel colours (RGB).
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2. Fixed partially transparent 32bpp pixels (RGB).
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- 1 byte length (values 0-63) + 64
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- 1 byte amount of opacity (0-255).
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- N x 3 byte pixel colours (RGB).
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3. Fixed fully transparent pixels.
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- 1 byte length (values 0-63) + 128
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4. Recolour layer.
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- 1 byte length (values 0-63) + 64 + 128
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- 1 byte layer to apply (0-255).
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- 1 byte amount of opacity (0-255).
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- N bytes table index.

‎SpriteEncoder/ast.cpp‎

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/*
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Copyright (c) 2013 Albert "Alberth" Hofkamp
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Permission is hereby granted, free of charge, to any person obtaining a copy of
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this software and associated documentation files (the "Software"), to deal in
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the Software without restriction, including without limitation the rights to
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use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
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of the Software, and to permit persons to whom the Software is furnished to do
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so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in all
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copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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SOFTWARE.
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*/
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#include <cstdio>
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#include <cstdlib>
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#include <cassert>
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#include "ast.h"
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#include "image.h"
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#include "output.h"
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enum Opacity
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{
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OP_TRANSPARENT = 0,
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OP_OPAQUE = 255,
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};
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const std::string sUnset = "<unset>";
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Sprite::Sprite()
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{
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m_iLine = -1;
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m_iSprite = -1;
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m_iLeft = -1;
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m_iTop = -1;
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m_iWidth = -1;
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m_iHeight = -1;
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m_sBaseImage = sUnset;
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m_sRecolourImage = sUnset;
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for (int i = 0; i < 256; i++)
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{
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m_aNumber[i] = i;
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}
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}
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void Sprite::SetRecolour(const std::string &sFilename)
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{
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m_sRecolourImage = sFilename;
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}
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static void Report(int iNumber, int iLine, const char *pMsg)
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{
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if (iNumber < 0)
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{
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fprintf(stderr, "Sprite at line %d: Missing %s\n", iLine, pMsg);
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exit(1);
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}
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}
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void Sprite::Check() const
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{
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Report(m_iSprite, m_iLine, "sprite number");
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Report(m_iLeft, m_iLine, "left edge coordinate");
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Report(m_iTop, m_iLine, "top edge coordinate");
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Report(m_iWidth, m_iLine, "sprite width");
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Report(m_iHeight, m_iLine, "sprite height");
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if (m_sBaseImage == sUnset)
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{
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fprintf(stderr, "Sprite at line %d: Missing image filename\n", m_iLine);
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exit(1);
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}
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}
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/**
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* Look ahead in the recolour bitmaps to check when the next recoloured pixels will occur.
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* @param iCount Current index in the image.
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* @param iEndCount End of the image.
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* @param pLayer Recolouring bitmap (if available).
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* @return Number of pixels to go before the next recoloured pixel (limited to 63 look ahead).
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*/
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static int GetDistanceToNextRecolour(const uint32 iCount, const uint32 iEndCount, const Image8bpp *pLayer)
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{
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uint32 iLength = iEndCount - iCount;
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if (iLength > 63) iLength = 63; // No need to look ahead further.
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if (pLayer != NULL)
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{
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for (size_t i = 0; i < iLength; i++)
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{
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if (pLayer->Get(iCount + i) != 0) return i;
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}
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}
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return iLength;
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}
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/**
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* Get the recolour table to use, and the number of pixels to recolour.
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* @param iCount Current index in the image.
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* @param iEndCount End of the image.
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* @param pLayer Recolouring bitmap.
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* @param pLayerNumber [out] Number of the recolouring table to use.
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* @return Number of pixels to recolour from the current position.
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*/
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static int GetRecolourInformation(const uint32 iCount, const uint32 iEndCount, const Image8bpp *pLayer, uint8 *pLayerNumber)
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{
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uint32 iLength = iEndCount - iCount;
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if (iLength > 63) iLength = 63; // No need to look ahead further.
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*pLayerNumber = pLayer->Get(iCount);
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for (size_t i = 1; i < iLength; i++)
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{
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if (pLayer->Get(iCount + i) != *pLayerNumber) return i;
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}
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return iLength;
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}
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/**
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* Look ahead in the base image to check how many pixels from the current position have the same opacity.
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* @param iCount Current index in the image.
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* @param iEndCount End of the image.
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* @parswm oBase Base image.
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* @return Number of pixels to go before the opacity of the current pixel changes (limited to 63 look ahead).
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*/
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static int GetDistanceToNextTransparency(const uint32 iCount, const uint32 iEndCount, const Image32bpp &oBase)
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{
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uint32 iLength = iEndCount - iCount;
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if (iLength > 63) iLength = 63; // No need to look ahead further.
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uint8 iOpacity = GetA(oBase.Get(iCount));
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for (uint i = 1; i < iLength; i++)
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{
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if (iOpacity != GetA(oBase.Get(iCount + i))) return i;
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}
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return iLength;
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}
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/**
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* Write the RGB colour for the next \a iLength pixels, starting from the \a iCount offset.
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* @param oBase Base image to encode.
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* @param iCount Current index in the image.
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* @param iLength Number of pixels to process.
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* @param pDest Destination to write to.
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*/
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static void WriteColour(const Image32bpp &oBase, uint32 iCount, int iLength, Output *pDest)
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{
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while (iLength > 0)
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{
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uint32 iColour = oBase.Get(iCount);
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iCount++;
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pDest->Uint8(GetR(iColour));
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pDest->Uint8(GetG(iColour));
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pDest->Uint8(GetB(iColour));
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iLength--;
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}
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}
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/**
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* Write the table index for the next \a iLength pixels, starting from the \a iCount offset.
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* @param oBase Base image to encode.
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* @param iCount Current index in the image.
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* @param iLength Number of pixels to process.
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* @param pDest Destination to write to.
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*/
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static void WriteTableIndex(const Image32bpp &oBase, uint32 iCount, int iLength, Output *pDest)
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{
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while (iLength > 0)
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{
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uint32 iColour = oBase.Get(iCount);
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iCount++;
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uint8 biggest = GetR(iColour);
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if (biggest < GetG(iColour)) biggest = GetG(iColour);
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if (biggest < GetB(iColour)) biggest = GetB(iColour);
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pDest->Uint8(biggest);
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iLength--;
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}
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}
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/**
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* Encode a 32bpp image from the \a oBase image, and optionally the recolouring \a pLayer bitmap.
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*/
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static void Encode32bpp(int iWidth, int iHeight, const Image32bpp &oBase, const Image8bpp *pLayer, Output *pDest, const unsigned char *pNumber)
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{
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const uint32 iPixCount = iWidth * iHeight;
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uint32 iCount = 0;
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while (iCount < iPixCount)
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{
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int iLength = GetDistanceToNextRecolour(iCount, iPixCount, pLayer);
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int length2 = GetDistanceToNextTransparency(iCount, iPixCount, oBase);
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if (iLength > 63) iLength = 63;
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if (iLength == 0) { // Recolour layer.
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uint8 iTableNumber;
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iLength = GetRecolourInformation(iCount, iPixCount, pLayer, &iTableNumber);
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if (length2 < iLength) iLength = length2;
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assert(iLength > 0);
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pDest->Uint8(64 + 128 + iLength);
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pDest->Uint8(pNumber[iTableNumber]);
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pDest->Uint8(GetA(oBase.Get(iCount))); // Opacity.
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WriteTableIndex(oBase, iCount, iLength, pDest);
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iCount += iLength;
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continue;
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}
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if (length2 < iLength) iLength = length2;
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assert(iLength > 0);
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uint8 iOpacity = GetA(oBase.Get(iCount));
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if (iOpacity == OP_OPAQUE) { // Fixed non-transparent 32bpp pixels (RGB).
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pDest->Uint8(iLength);
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WriteColour(oBase, iCount, iLength, pDest);
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iCount += iLength;
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continue;
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}
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if (iOpacity == OP_TRANSPARENT) { // Fixed fully transparent pixels.
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pDest->Uint8(128 + iLength);
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iCount += iLength;
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continue;
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}
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/* Partially transparent 32bpp pixels (RGB). */
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pDest->Uint8(64 + iLength);
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pDest->Uint8(iOpacity);
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WriteColour(oBase, iCount, iLength, pDest);
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iCount += iLength;
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continue;
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}
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}
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void Sprite::Write(Output *pOut) const
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{
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Image32bpp *pBase = Load32Bpp(m_sBaseImage, m_iLine, m_iLeft, m_iWidth, m_iTop, m_iHeight);
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if (pBase == NULL)
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{
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fprintf(stderr, "Warning: Skipping sprite %d at line %d: Image load failed.\n", m_iSprite, m_iLine);
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return;
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}
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Image8bpp *pLayer = NULL;
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if (m_sRecolourImage != sUnset)
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{
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pLayer = Load8Bpp(m_sRecolourImage, m_iLine, m_iLeft, m_iWidth, m_iTop, m_iHeight);
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}
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int iAddress = pOut->Reserve(4);
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pOut->Uint16(m_iSprite);
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pOut->Uint16(m_iWidth);
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pOut->Uint16(m_iHeight); // XXX Add length of this sprite?
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Encode32bpp(m_iWidth, m_iHeight, *pBase, pLayer, pOut, m_aNumber);
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int iLength = pOut->Reserve(0) - (iAddress + 4); // Start counting after the length.
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pOut->Write(iAddress, iLength & 0xFF);
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pOut->Write(iAddress + 1, (iLength >> 8) & 0xFF);
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pOut->Write(iAddress + 2, (iLength >> 16) & 0xFF);
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pOut->Write(iAddress + 3, (iLength >> 24) & 0xFF);
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delete pLayer;
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delete pBase;
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}
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// vim: et sw=4 ts=4 sts=4

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