/* $Revision: 1.7 $ */ /* Copyright 1984-2000 The MathWorks, Inc. */ /* * BMPDRLE --- decode RLE-compressed data in a BMP file * * OUT = BMPDRLE(IN, WIDTH, HEIGHT, METHOD) * * IN is a uint8 array containing the byte-stream read in from the file. * * WIDTH, HEIGHT are the expected image dimensions; these are obtained from * the header information. * * METHOD is either 'rle4' or 'rle8'. * * OUT is a uint8 array containing the decompressed byte-stream. * * Reference: Murray and vanRyper, Encyclopedia of Graphics File Formats, * 2nd ed, O'Reilly. */ static char rcsid[] = "$Id: bmpdrle.c,v 1.7 2000/06/01 04:17:12 joeya Exp $"; #include #include "mex.h" #define RLE4 (1) #define RLE8 (2) #define LSN(value) ((value) & 0x0f) /* least-significant nibble */ #define MSN(value) (((uint8_T) ((value) & 0xf0)) >> 4) /* most-significant */ /* * ValidateInput --- input argument-parsing and error checking * * Inputs: nlhs --- number of left-side arguments * nrhs --- number of right-side arguments * prhs --- array of right-side arguments * * Outputs: width --- expected image width * height --- expected image height * method --- RLE4 or RLE8 * * Return: none */ void ValidateInput(int nlhs, int nrhs, const mxArray *prhs[], int *width, int *height, int *method) { char *methodString; int strLength; if (nlhs > 1) { mexErrMsgTxt("Too many output arguments"); } if (nrhs < 4) { mexErrMsgTxt("Too few input arguments"); } if (nrhs > 4) { mexErrMsgTxt("Too many input arguments"); } if (!mxIsUint8(prhs[0])) { mexErrMsgTxt("First input argument must be uint8"); } if (!mxIsDouble(prhs[1])) { mexErrMsgTxt("Second input argument must be a double scalar"); } if (!mxIsDouble(prhs[2])) { mexErrMsgTxt("Third input argument must be a double scalar"); } if (!mxIsChar(prhs[3])) { mexErrMsgTxt("Fourth input argument must be a string"); } *width = (int) *((double *) mxGetPr(prhs[1])); *height = (int) *((double *) mxGetPr(prhs[2])); if ((*width < 0) || (*height < 0)) { mexErrMsgTxt("Width and height must be nonnegative"); } strLength = mxGetM(prhs[3]) * mxGetN(prhs[3]) * sizeof(mxChar); methodString = mxCalloc(strLength + 1, sizeof(char)); mxGetString(prhs[3], methodString, strLength + 1); if (strcmp(methodString, "rle4") == 0) { *method = RLE4; } else if (strcmp(methodString, "rle8") == 0) { *method = RLE8; } else { mexErrMsgTxt("Second input argument must be ""rle4"" or ""rle8"""); } } #define CHK_OUT_BUFFER \ if (outBufferIndex >= outBufferSize) { \ mexWarnMsgTxt("Apparent RLE decoding failure; BMP file may be corrupt"); \ inBufferIndex = inBufferSize; \ continue; \ } \ if (outBufferIndex < 0) { \ mexErrMsgTxt("RLE decoding failure; BMP file may be corrupt"); \ } #define CHK_IN_BUFFER \ if (inBufferIndex >= inBufferSize) { \ mexWarnMsgTxt("Apparent RLE decoding failure; BMP file may be truncated");\ inBufferIndex = inBufferSize; \ continue; \ } /* * bmpDecode --- decode rle-encoded byte stream * This routine is used for both 4-bit RLE and 8-bit RLE * * Inputs: outBufferSize --- allocated size of outBuffer in bytes * width --- expected image width * height --- expected image height * method --- RLE4 or RLE8 * inBuffer --- input compressed byte-stream * inBufferSize --- length of input byte-stream in bytes * * Outputs: outBuffer --- decompressed byte-stream; must be preallocated * * Return: none */ void bmpDecode(uint8_T *outBuffer, int outBufferSize, int width, int height, int method, uint8_T *inBuffer, int inBufferSize) { uint8_T runCount; uint8_T runValue; uint8_T value1; uint8_T value2; int32_T inBufferIndex = 0; int32_T outBufferIndex = 0; int32_T currentRow = 0; int32_T currentColumn = 0; int k; bool endOfBitmapFound = false; while (inBufferIndex < inBufferSize) { CHK_IN_BUFFER; runCount = (int32_T) inBuffer[inBufferIndex++]; CHK_IN_BUFFER; runValue = inBuffer[inBufferIndex++]; switch (runCount) { case 0: switch (runValue) { case 0: /* end-of-scanline escape code */ currentRow = 0; currentColumn++; outBufferIndex = currentColumn * width + currentRow; break; case 1: /* end-of-bitmap escape code */ if (inBufferIndex < inBufferSize) { mexWarnMsgTxt("End-of-bitmap code encountered " "before end of data"); inBufferIndex = inBufferSize; continue; } endOfBitmapFound = true; break; case 2: /* delta escape code */ CHK_IN_BUFFER; currentRow += inBuffer[inBufferIndex++]; CHK_IN_BUFFER; currentColumn -= inBuffer[inBufferIndex++]; /* BMP "width" is MATLAB's height because we're reading */ /* into a column-major array. */ outBufferIndex = currentColumn * width + currentRow; break; default: /* literal run */ if (method == RLE8) { for (k = 0; k < (int) runValue/2; k++) { /* Read 2 bytes from input buffer */ CHK_IN_BUFFER; value1 = inBuffer[inBufferIndex++]; CHK_IN_BUFFER; value2 = inBuffer[inBufferIndex++]; CHK_OUT_BUFFER; outBuffer[outBufferIndex++] = value1; currentRow++; CHK_OUT_BUFFER; outBuffer[outBufferIndex++] = value2; currentRow++; } if ((runValue % 2) != 0) { /* Read 2 bytes from input buffer */ CHK_IN_BUFFER; value1 = inBuffer[inBufferIndex++]; CHK_IN_BUFFER; value2 = inBuffer[inBufferIndex++]; /* only first value gets used */ CHK_OUT_BUFFER; outBuffer[outBufferIndex++] = value1; } } else { /* decoding is broken up below because runs */ /* must be word-aligned */ for (k = 0; k < (int) runValue/4; k++) { /* Read 2 bytes from input buffer */ CHK_IN_BUFFER; value1 = inBuffer[inBufferIndex++]; CHK_IN_BUFFER; value2 = inBuffer[inBufferIndex++]; /* put 4 values into the output buffer */ CHK_OUT_BUFFER; outBuffer[outBufferIndex++] = MSN(value1); currentRow++; CHK_OUT_BUFFER; outBuffer[outBufferIndex++] = LSN(value1); currentRow++; CHK_OUT_BUFFER; outBuffer[outBufferIndex++] = MSN(value2); currentRow++; CHK_OUT_BUFFER; outBuffer[outBufferIndex++] = LSN(value2); currentRow++; } if ((runValue % 4) != 0) { /* Read 2 bytes from input buffer */ CHK_IN_BUFFER; value1 = inBuffer[inBufferIndex++]; CHK_IN_BUFFER; value2 = inBuffer[inBufferIndex++]; CHK_OUT_BUFFER; outBuffer[outBufferIndex++] = MSN(value1); currentRow++; if ((int) (runValue % 4) > 1) { CHK_OUT_BUFFER; outBuffer[outBufferIndex++] = LSN(value1); currentRow++; } if ((int) (runValue % 4) > 2) { CHK_OUT_BUFFER; outBuffer[outBufferIndex++] = MSN(value2); } } } } break; default: /* encoded run */ if (method == RLE4) { /* alternate writing the most-significant and * least-significant nibble to the buffer */ for (k = 0; k < (int) runCount/2; k++) { CHK_OUT_BUFFER; outBuffer[outBufferIndex++] = MSN(runValue); currentRow++; CHK_OUT_BUFFER; outBuffer[outBufferIndex++] = LSN(runValue); currentRow++; } if ((runCount % 2) != 0) { /* odd-length run */ CHK_OUT_BUFFER; outBuffer[outBufferIndex++] = MSN(runValue); currentRow++; } } else { /* write an 8-bit value */ while (runCount--) { CHK_OUT_BUFFER; outBuffer[outBufferIndex++] = runValue; } } break; } } if (!endOfBitmapFound) { mexWarnMsgTxt("No end-of-bitmap code; BMP file may be truncated"); } } void mexFunction(int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[]) { int width; int height; int method; int inputBufferLength; int outputBufferLength; uint8_T *inputBuffer; uint8_T *outputBuffer; mxArray *Out; int outputSize[2]; ValidateInput(nlhs, nrhs, prhs, &width, &height, &method); outputSize[0] = width; outputSize[1] = height; Out = mxCreateNumericArray(2, outputSize, mxUINT8_CLASS, mxREAL); outputBuffer = (uint8_T *) mxGetPr(Out); outputBufferLength = width * height; inputBuffer = (uint8_T *) mxGetPr(prhs[0]); inputBufferLength = mxGetM(prhs[0]) * mxGetN(prhs[0]); bmpDecode(outputBuffer, outputBufferLength, width, height, method, inputBuffer, inputBufferLength); plhs[0] = Out; }