Add tiny JPEG decoder library

1 files changed, 286 insertions, 0 deletions

diff --git a/com32/lib/jpeg/jidctflt.c b/com32/lib/jpeg/jidctflt.c
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+++ b/com32/lib/jpeg/jidctflt.c
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+/*
+ * jidctflt.c
+ *
+ * Copyright (C) 1994-1998, Thomas G. Lane.
+ * This file is part of the Independent JPEG Group's software.
+ *
+ * The authors make NO WARRANTY or representation, either express or implied,
+ * with respect to this software, its quality, accuracy, merchantability, or 
+ * fitness for a particular purpose.  This software is provided "AS IS", and you,
+ * its user, assume the entire risk as to its quality and accuracy.
+ *
+ * This software is copyright (C) 1991-1998, Thomas G. Lane.
+ * All Rights Reserved except as specified below.
+ *
+ * Permission is hereby granted to use, copy, modify, and distribute this
+ * software (or portions thereof) for any purpose, without fee, subject to these
+ * conditions:
+ * (1) If any part of the source code for this software is distributed, then this
+ * README file must be included, with this copyright and no-warranty notice
+ * unaltered; and any additions, deletions, or changes to the original files
+ * must be clearly indicated in accompanying documentation.
+ * (2) If only executable code is distributed, then the accompanying
+ * documentation must state that "this software is based in part on the work of
+ * the Independent JPEG Group".
+ * (3) Permission for use of this software is granted only if the user accepts
+ * full responsibility for any undesirable consequences; the authors accept
+ * NO LIABILITY for damages of any kind.
+ * 
+ * These conditions apply to any software derived from or based on the IJG code,
+ * not just to the unmodified library.  If you use our work, you ought to
+ * acknowledge us.
+ * 
+ * Permission is NOT granted for the use of any IJG author's name or company name
+ * in advertising or publicity relating to this software or products derived from
+ * it.  This software may be referred to only as "the Independent JPEG Group's
+ * software".
+ * 
+ * We specifically permit and encourage the use of this software as the basis of
+ * commercial products, provided that all warranty or liability claims are
+ * assumed by the product vendor.
+ *
+ *
+ * This file contains a floating-point implementation of the
+ * inverse DCT (Discrete Cosine Transform).  In the IJG code, this routine
+ * must also perform dequantization of the input coefficients.
+ *
+ * This implementation should be more accurate than either of the integer
+ * IDCT implementations.  However, it may not give the same results on all
+ * machines because of differences in roundoff behavior.  Speed will depend
+ * on the hardware's floating point capacity.
+ *
+ * A 2-D IDCT can be done by 1-D IDCT on each column followed by 1-D IDCT
+ * on each row (or vice versa, but it's more convenient to emit a row at
+ * a time).  Direct algorithms are also available, but they are much more
+ * complex and seem not to be any faster when reduced to code.
+ *
+ * This implementation is based on Arai, Agui, and Nakajima's algorithm for
+ * scaled DCT.  Their original paper (Trans. IEICE E-71(11):1095) is in
+ * Japanese, but the algorithm is described in the Pennebaker & Mitchell
+ * JPEG textbook (see REFERENCES section in file README).  The following code
+ * is based directly on figure 4-8 in P&M.
+ * While an 8-point DCT cannot be done in less than 11 multiplies, it is
+ * possible to arrange the computation so that many of the multiplies are
+ * simple scalings of the final outputs.  These multiplies can then be
+ * folded into the multiplications or divisions by the JPEG quantization
+ * table entries.  The AA&N method leaves only 5 multiplies and 29 adds
+ * to be done in the DCT itself.
+ * The primary disadvantage of this method is that with a fixed-point
+ * implementation, accuracy is lost due to imprecise representation of the
+ * scaled quantization values.  However, that problem does not arise if
+ * we use floating point arithmetic.
+ */
+
+#include <stdint.h>
+#include "tinyjpeg-internal.h"
+
+#define FAST_FLOAT float
+#define DCTSIZE	   8
+#define DCTSIZE2   (DCTSIZE*DCTSIZE)
+
+#define DEQUANTIZE(coef,quantval)  (((FAST_FLOAT) (coef)) * (quantval))
+
+#if defined(__GNUC__) && defined(__i686__) || defined(__x86_64__) 
+
+static inline unsigned char descale_and_clamp(int x, int shift)
+{
+  __asm__ (
+      "add %3,%1\n"
+      "\tsar %2,%1\n"
+      "\tsub $-128,%1\n"
+      "\tcmovl %5,%1\n"	/* Use the sub to compare to 0 */
+      "\tcmpl %4,%1\n" 
+      "\tcmovg %4,%1\n"
+      : "=r"(x) 
+      : "0"(x), "i"(shift), "i"(1UL<<(shift-1)), "r" (0xff), "r" (0)
+      );
+  return x;
+}
+
+#else
+static inline unsigned char descale_and_clamp(int x, int shift)
+{
+  x += (1UL<<(shift-1));
+  if (x<0)
+    x = (x >> shift) | ((~(0UL)) << (32-(shift)));
+  else
+    x >>= shift;
+  x += 128;
+  if (x>255)
+    return 255;
+  else if (x<0)
+    return 0;
+  else 
+    return x;
+}
+#endif
+
+/*
+ * Perform dequantization and inverse DCT on one block of coefficients.
+ */
+
+void
+jpeg_idct_float (struct component *compptr, uint8_t *output_buf, int stride)
+{
+  FAST_FLOAT tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7;
+  FAST_FLOAT tmp10, tmp11, tmp12, tmp13;
+  FAST_FLOAT z5, z10, z11, z12, z13;
+  int16_t *inptr;
+  FAST_FLOAT *quantptr;
+  FAST_FLOAT *wsptr;
+  uint8_t *outptr;
+  int ctr;
+  FAST_FLOAT workspace[DCTSIZE2]; /* buffers data between passes */
+
+  /* Pass 1: process columns from input, store into work array. */
+
+  inptr = compptr->DCT;
+  quantptr = compptr->Q_table;
+  wsptr = workspace;
+  for (ctr = DCTSIZE; ctr > 0; ctr--) {
+    /* Due to quantization, we will usually find that many of the input
+     * coefficients are zero, especially the AC terms.  We can exploit this
+     * by short-circuiting the IDCT calculation for any column in which all
+     * the AC terms are zero.  In that case each output is equal to the
+     * DC coefficient (with scale factor as needed).
+     * With typical images and quantization tables, half or more of the
+     * column DCT calculations can be simplified this way.
+     */
+    
+    if (inptr[DCTSIZE*1] == 0 && inptr[DCTSIZE*2] == 0 &&
+	inptr[DCTSIZE*3] == 0 && inptr[DCTSIZE*4] == 0 &&
+	inptr[DCTSIZE*5] == 0 && inptr[DCTSIZE*6] == 0 &&
+	inptr[DCTSIZE*7] == 0) {
+      /* AC terms all zero */
+      FAST_FLOAT dcval = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]);
+      
+      wsptr[DCTSIZE*0] = dcval;
+      wsptr[DCTSIZE*1] = dcval;
+      wsptr[DCTSIZE*2] = dcval;
+      wsptr[DCTSIZE*3] = dcval;
+      wsptr[DCTSIZE*4] = dcval;
+      wsptr[DCTSIZE*5] = dcval;
+      wsptr[DCTSIZE*6] = dcval;
+      wsptr[DCTSIZE*7] = dcval;
+      
+      inptr++;			/* advance pointers to next column */
+      quantptr++;
+      wsptr++;
+      continue;
+    }
+    
+    /* Even part */
+
+    tmp0 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]);
+    tmp1 = DEQUANTIZE(inptr[DCTSIZE*2], quantptr[DCTSIZE*2]);
+    tmp2 = DEQUANTIZE(inptr[DCTSIZE*4], quantptr[DCTSIZE*4]);
+    tmp3 = DEQUANTIZE(inptr[DCTSIZE*6], quantptr[DCTSIZE*6]);
+
+    tmp10 = tmp0 + tmp2;	/* phase 3 */
+    tmp11 = tmp0 - tmp2;
+
+    tmp13 = tmp1 + tmp3;	/* phases 5-3 */
+    tmp12 = (tmp1 - tmp3) * ((FAST_FLOAT) 1.414213562) - tmp13; /* 2*c4 */
+
+    tmp0 = tmp10 + tmp13;	/* phase 2 */
+    tmp3 = tmp10 - tmp13;
+    tmp1 = tmp11 + tmp12;
+    tmp2 = tmp11 - tmp12;
+    
+    /* Odd part */
+
+    tmp4 = DEQUANTIZE(inptr[DCTSIZE*1], quantptr[DCTSIZE*1]);
+    tmp5 = DEQUANTIZE(inptr[DCTSIZE*3], quantptr[DCTSIZE*3]);
+    tmp6 = DEQUANTIZE(inptr[DCTSIZE*5], quantptr[DCTSIZE*5]);
+    tmp7 = DEQUANTIZE(inptr[DCTSIZE*7], quantptr[DCTSIZE*7]);
+
+    z13 = tmp6 + tmp5;		/* phase 6 */
+    z10 = tmp6 - tmp5;
+    z11 = tmp4 + tmp7;
+    z12 = tmp4 - tmp7;
+
+    tmp7 = z11 + z13;		/* phase 5 */
+    tmp11 = (z11 - z13) * ((FAST_FLOAT) 1.414213562); /* 2*c4 */
+
+    z5 = (z10 + z12) * ((FAST_FLOAT) 1.847759065); /* 2*c2 */
+    tmp10 = ((FAST_FLOAT) 1.082392200) * z12 - z5; /* 2*(c2-c6) */
+    tmp12 = ((FAST_FLOAT) -2.613125930) * z10 + z5; /* -2*(c2+c6) */
+
+    tmp6 = tmp12 - tmp7;	/* phase 2 */
+    tmp5 = tmp11 - tmp6;
+    tmp4 = tmp10 + tmp5;
+
+    wsptr[DCTSIZE*0] = tmp0 + tmp7;
+    wsptr[DCTSIZE*7] = tmp0 - tmp7;
+    wsptr[DCTSIZE*1] = tmp1 + tmp6;
+    wsptr[DCTSIZE*6] = tmp1 - tmp6;
+    wsptr[DCTSIZE*2] = tmp2 + tmp5;
+    wsptr[DCTSIZE*5] = tmp2 - tmp5;
+    wsptr[DCTSIZE*4] = tmp3 + tmp4;
+    wsptr[DCTSIZE*3] = tmp3 - tmp4;
+
+    inptr++;			/* advance pointers to next column */
+    quantptr++;
+    wsptr++;
+  }
+  
+  /* Pass 2: process rows from work array, store into output array. */
+  /* Note that we must descale the results by a factor of 8 == 2**3. */
+
+  wsptr = workspace;
+  outptr = output_buf;
+  for (ctr = 0; ctr < DCTSIZE; ctr++) {
+    /* Rows of zeroes can be exploited in the same way as we did with columns.
+     * However, the column calculation has created many nonzero AC terms, so
+     * the simplification applies less often (typically 5% to 10% of the time).
+     * And testing floats for zero is relatively expensive, so we don't bother.
+     */
+    
+    /* Even part */
+
+    tmp10 = wsptr[0] + wsptr[4];
+    tmp11 = wsptr[0] - wsptr[4];
+
+    tmp13 = wsptr[2] + wsptr[6];
+    tmp12 = (wsptr[2] - wsptr[6]) * ((FAST_FLOAT) 1.414213562) - tmp13;
+
+    tmp0 = tmp10 + tmp13;
+    tmp3 = tmp10 - tmp13;
+    tmp1 = tmp11 + tmp12;
+    tmp2 = tmp11 - tmp12;
+
+    /* Odd part */
+
+    z13 = wsptr[5] + wsptr[3];
+    z10 = wsptr[5] - wsptr[3];
+    z11 = wsptr[1] + wsptr[7];
+    z12 = wsptr[1] - wsptr[7];
+
+    tmp7 = z11 + z13;
+    tmp11 = (z11 - z13) * ((FAST_FLOAT) 1.414213562);
+
+    z5 = (z10 + z12) * ((FAST_FLOAT) 1.847759065); /* 2*c2 */
+    tmp10 = ((FAST_FLOAT) 1.082392200) * z12 - z5; /* 2*(c2-c6) */
+    tmp12 = ((FAST_FLOAT) -2.613125930) * z10 + z5; /* -2*(c2+c6) */
+
+    tmp6 = tmp12 - tmp7;
+    tmp5 = tmp11 - tmp6;
+    tmp4 = tmp10 + tmp5;
+
+    /* Final output stage: scale down by a factor of 8 and range-limit */
+
+    outptr[0] = descale_and_clamp(tmp0 + tmp7, 3);
+    outptr[7] = descale_and_clamp(tmp0 - tmp7, 3);
+    outptr[1] = descale_and_clamp(tmp1 + tmp6, 3);
+    outptr[6] = descale_and_clamp(tmp1 - tmp6, 3);
+    outptr[2] = descale_and_clamp(tmp2 + tmp5, 3);
+    outptr[5] = descale_and_clamp(tmp2 - tmp5, 3);
+    outptr[4] = descale_and_clamp(tmp3 + tmp4, 3);
+    outptr[3] = descale_and_clamp(tmp3 - tmp4, 3);
+
+    
+    wsptr += DCTSIZE;		/* advance pointer to next row */
+    outptr += stride;
+  }
+}
+