* 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 DCTSIZE2 (DCTSIZE * DCTSIZE)
-#define DEQUANTIZE(coef,quantval) (((FAST_FLOAT) (coef)) * (quantval))
+#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), "Ic"((unsigned char)shift), "ir"(1U<<(shift-1)), "r" (0xff), "r" (0)
- );
- return x;
+ __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), "Ic"((unsigned char)shift), "ir" (1U << (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;
+ x += 1UL << (shift - 1);
+ if (x < 0)
+ x = (x >> shift) | ((~(0UL)) << (32 - (shift)));
+ else
+ x >>= shift;
+ x += 128;
+ if (x > 255)
+ return 255;
+ if (x < 0)
+ return 0;
+ return x;
}
#endif
* Perform dequantization and inverse DCT on one block of coefficients.
*/
-void
-tinyjpeg_idct_float (struct component *compptr, uint8_t *output_buf, int stride)
+void tinyjpeg_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 */
+ 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((int)(tmp0 + tmp7), 3);
- outptr[7] = descale_and_clamp((int)(tmp0 - tmp7), 3);
- outptr[1] = descale_and_clamp((int)(tmp1 + tmp6), 3);
- outptr[6] = descale_and_clamp((int)(tmp1 - tmp6), 3);
- outptr[2] = descale_and_clamp((int)(tmp2 + tmp5), 3);
- outptr[5] = descale_and_clamp((int)(tmp2 - tmp5), 3);
- outptr[4] = descale_and_clamp((int)(tmp3 + tmp4), 3);
- outptr[3] = descale_and_clamp((int)(tmp3 - tmp4), 3);
-
-
- wsptr += DCTSIZE; /* advance pointer to next row */
- outptr += stride;
- }
+ outptr[0] = descale_and_clamp((int)(tmp0 + tmp7), 3);
+ outptr[7] = descale_and_clamp((int)(tmp0 - tmp7), 3);
+ outptr[1] = descale_and_clamp((int)(tmp1 + tmp6), 3);
+ outptr[6] = descale_and_clamp((int)(tmp1 - tmp6), 3);
+ outptr[2] = descale_and_clamp((int)(tmp2 + tmp5), 3);
+ outptr[5] = descale_and_clamp((int)(tmp2 - tmp5), 3);
+ outptr[4] = descale_and_clamp((int)(tmp3 + tmp4), 3);
+ outptr[3] = descale_and_clamp((int)(tmp3 - tmp4), 3);
+
+
+ wsptr += DCTSIZE; /* advance pointer to next row */
+ outptr += stride;
+ }
}