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//-----------------------------------------------------------------------------
// Description: Functions for run-length encoding
//-----------------------------------------------------------------------------
// RLE code from TrueVision's TGA sample code available as Tgautils.zip at
// ftp://ftp.truevision.com/pub/TGA.File.Format.Spec/PC.Version
#define IL_RLE_C
#include "il_internal.h"
#include "il_rle.h"
ILboolean ilRleCompressLine(ILubyte *p, ILuint n, ILubyte bpp,
ILubyte *q, ILuint *DestWidth, ILenum CompressMode) {
ILint DiffCount; // pixel count until two identical
ILint SameCount; // number of identical adjacent pixels
ILint RLEBufSize = 0; // count of number of bytes encoded
ILint MaxRun;
const ILint bmp_pad_to_even = (ILint)(1 - ((ILint)q - *DestWidth) % 2);
switch( CompressMode ) {
case IL_TGACOMP:
MaxRun = TGA_MAX_RUN;
break;
case IL_SGICOMP:
MaxRun = SGI_MAX_RUN;
break;
case IL_BMPCOMP:
MaxRun = BMP_MAX_RUN;
break;
default:
ilSetError(IL_INVALID_PARAM);
return IL_FALSE;
}
while( n > 0 ) {
// Analyze pixels
DiffCount = CountDiffPixels(p, bpp, (ILint)n > MaxRun ? MaxRun : n);
SameCount = CountSamePixels(p, bpp, (ILint)n > MaxRun ? MaxRun : n);
if( CompressMode == IL_BMPCOMP ) {
ILint remaining_data = n - DiffCount - SameCount;
if( remaining_data < 3 ) { // check if the run has gone near the end
// no absolute run can be done
// complete the line adding 0x01 + pixel, for each pixel
while( remaining_data > 0 ) {
*q++ = 0x01;
*q++ = *p++;
remaining_data--;
}
DiffCount = 0;
SameCount = 0;
n = 0;
}
}
if( DiffCount > 0 ) { // create a raw packet (bmp absolute run)
switch(CompressMode) {
case IL_TGACOMP:
*q++ = (ILbyte)(DiffCount - 1);
break;
case IL_BMPCOMP:
*q++ = 0x00; RLEBufSize++;
*q++ = (ILbyte)DiffCount;
break;
case IL_SGICOMP:
*q++ = (ILbyte)(DiffCount | 0x80);
break;
}
n -= DiffCount;
RLEBufSize += (DiffCount * bpp) + 1;
while( DiffCount > 0 ) {
switch(bpp) {
case 4: *q++ = *p++;
case 3: *q++ = *p++;
case 2: *q++ = *p++;
case 1: *q++ = *p++;
}
DiffCount--;
}
if( CompressMode == IL_BMPCOMP ) {
if( (size_t)q % 2 == bmp_pad_to_even ) {
*q++ = 0x00; // insert padding
}
}
}
if( SameCount > 1 ) { // create a RLE packet
switch(CompressMode) {
case IL_TGACOMP:
*q++ = (ILbyte)((SameCount - 1) | 0x80);
break;
case IL_SGICOMP:
case IL_BMPCOMP:
*q++ = (ILbyte)(SameCount);
break;
}
n -= SameCount;
RLEBufSize += bpp + 1;
p += (SameCount - 1) * bpp;
*q++ = *p++;
switch(bpp) {
case 4: *q++ = *p++;
case 3: *q++ = *p++;
case 2: *q++ = *p++;
case 1: *q++ = *p++;
}
}
}
// write line termination code
switch(CompressMode) {
case IL_SGICOMP:
++RLEBufSize;
*q++ = 0;
break;
case IL_BMPCOMP:
*q++ = 0x00; RLEBufSize++;
*q++ = 0x00; RLEBufSize++;
break;
}
*DestWidth = RLEBufSize;
return IL_TRUE;
}
// Compresses an entire image using run-length encoding
ILuint ilRleCompress(ILubyte *Data, ILuint Width, ILuint Height, ILuint Depth, ILubyte Bpp,
ILubyte *Dest, ILenum CompressMode, ILuint *ScanTable) {
ILuint DestW = 0, i, j, LineLen, Bps = Width * Bpp, SizeOfPlane = Width * Height * Bpp;
if( ScanTable )
imemclear(ScanTable,Depth*Height*sizeof(ILuint));
for( j = 0; j < Depth; j++ ) {
for( i = 0; i < Height; i++ ) {
if( ScanTable )
*ScanTable++ = DestW;
ilRleCompressLine(Data + j * SizeOfPlane + i * Bps, Width, Bpp, Dest + DestW, &LineLen, CompressMode);
DestW += LineLen;
}
}
if( CompressMode == IL_BMPCOMP ) { // add end of image
*(Data+DestW) = 0x00; DestW++;
*(Data+DestW) = 0x01; DestW++;
}
return DestW;
}
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