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--- jcdctmgr.c.orig 2015-05-18 16:28:09.000000000 +0200 |
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+++ jcdctmgr.c 2015-08-30 02:21:25.079140000 +0200 |
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@@ -6,7 +6,7 @@ |
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* libjpeg-turbo Modifications: |
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* Copyright (C) 1999-2006, MIYASAKA Masaru. |
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* Copyright 2009 Pierre Ossman <ossman@cendio.se> for Cendio AB |
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- * Copyright (C) 2011, 2014 D. R. Commander |
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+ * Copyright (C) 2011, 2014-2015 D. R. Commander |
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* mozjpeg Modifications: |
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* Copyright (C) 2014, Mozilla Corporation. |
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* For conditions of distribution and use, see the accompanying README file. |
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@@ -185,6 +185,19 @@ compute_reciprocal (UINT16 divisor, DCTE |
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UDCTELEM c; |
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int b, r; |
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|
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+ if (divisor == 1) { |
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+ /* divisor == 1 means unquantized, so these reciprocal/correction/shift |
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+ * values will cause the C quantization algorithm to act like the |
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+ * identity function. Since only the C quantization algorithm is used in |
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+ * these cases, the scale value is irrelevant. |
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+ */ |
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+ dtbl[DCTSIZE2 * 0] = (DCTELEM) 1; /* reciprocal */ |
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+ dtbl[DCTSIZE2 * 1] = (DCTELEM) 0; /* correction */ |
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+ dtbl[DCTSIZE2 * 2] = (DCTELEM) 1; /* scale */ |
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+ dtbl[DCTSIZE2 * 3] = (DCTELEM) (-sizeof(DCTELEM) * 8); /* shift */ |
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+ return 0; |
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+ } |
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+ |
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b = flss(divisor) - 1; |
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r = sizeof(DCTELEM) * 8 + b; |
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|
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@@ -589,7 +602,8 @@ quantize (JCOEFPTR coef_block, DCTELEM * |
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|
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#if BITS_IN_JSAMPLE == 8 |
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|
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- UDCTELEM recip, corr, shift; |
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+ UDCTELEM recip, corr; |
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+ int shift; |
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UDCTELEM2 product; |
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|
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for (i = 0; i < DCTSIZE2; i++) { |