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Simplify indexing 

TODO: Allocations!
pull/298/head
James Jackson-South 9 years ago
parent
8c22c11408
commit
a236a80666
1 changed files with 35 additions and 45 deletions
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  1. 80
      src/ImageSharp/Formats/Jpeg/Port/Components/IDCT.cs

80
src/ImageSharp/Formats/Jpeg/Port/Components/IDCT.cs
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@ -331,22 +331,19 @@
int p0, p1, p2, p3, p4, p5, p6, p7; int p0, p1, p2, p3, p4, p5, p6, p7;
int coefBlockIndex = 0; for (int col = 0; col < 8; col++)
int workspaceIndex = 0;
int quantTableIndex = 0;
for (int col = 8; col > 0; col--)
{ {
// Gather block data // Gather block data
p0 = blockData[coefBlockIndex]; p0 = blockData[col];
p1 = blockData[coefBlockIndex + 8]; p1 = blockData[col + 8];
p2 = blockData[coefBlockIndex + 16]; p2 = blockData[col + 16];
p3 = blockData[coefBlockIndex + 24]; p3 = blockData[col + 24];
p4 = blockData[coefBlockIndex + 32]; p4 = blockData[col + 32];
p5 = blockData[coefBlockIndex + 40]; p5 = blockData[col + 40];
p6 = blockData[coefBlockIndex + 48]; p6 = blockData[col + 48];
p7 = blockData[coefBlockIndex + 56]; p7 = blockData[col + 56];
int tmp0 = p0 * multiplierSpan[quantTableIndex]; int tmp0 = p0 * multiplierSpan[col];
// Due to quantization, we will usually find that many of the input // Due to quantization, we will usually find that many of the input
// coefficients are zero, especially the AC terms. We can exploit this // coefficients are zero, especially the AC terms. We can exploit this
@ -359,25 +356,22 @@
{ {
short dcval = (short)tmp0; short dcval = (short)tmp0;
computationBufferSpan[workspaceIndex] = dcval; computationBufferSpan[col] = dcval;
computationBufferSpan[workspaceIndex + 8] = dcval; computationBufferSpan[col + 8] = dcval;
computationBufferSpan[workspaceIndex + 16] = dcval; computationBufferSpan[col + 16] = dcval;
computationBufferSpan[workspaceIndex + 24] = dcval; computationBufferSpan[col + 24] = dcval;
computationBufferSpan[workspaceIndex + 32] = dcval; computationBufferSpan[col + 32] = dcval;
computationBufferSpan[workspaceIndex + 40] = dcval; computationBufferSpan[col + 40] = dcval;
computationBufferSpan[workspaceIndex + 48] = dcval; computationBufferSpan[col + 48] = dcval;
computationBufferSpan[workspaceIndex + 56] = dcval; computationBufferSpan[col + 56] = dcval;
coefBlockIndex++;
quantTableIndex++;
workspaceIndex++;
continue; continue;
} }
// Even part // Even part
int tmp1 = p2 * multiplierSpan[quantTableIndex + 16]; int tmp1 = p2 * multiplierSpan[col + 16];
int tmp2 = p4 * multiplierSpan[quantTableIndex + 32]; int tmp2 = p4 * multiplierSpan[col + 32];
int tmp3 = p6 * multiplierSpan[quantTableIndex + 48]; int tmp3 = p6 * multiplierSpan[col + 48];
int tmp10 = tmp0 + tmp2; // Phase 3 int tmp10 = tmp0 + tmp2; // Phase 3
int tmp11 = tmp0 - tmp2; int tmp11 = tmp0 - tmp2;
@ -391,10 +385,10 @@
tmp2 = tmp11 - tmp12; tmp2 = tmp11 - tmp12;
// Odd Part // Odd Part
int tmp4 = p1 * multiplierSpan[quantTableIndex + 8]; int tmp4 = p1 * multiplierSpan[col + 8];
int tmp5 = p3 * multiplierSpan[quantTableIndex + 24]; int tmp5 = p3 * multiplierSpan[col + 24];
int tmp6 = p5 * multiplierSpan[quantTableIndex + 40]; int tmp6 = p5 * multiplierSpan[col + 40];
int tmp7 = p7 * multiplierSpan[quantTableIndex + 56]; int tmp7 = p7 * multiplierSpan[col + 56];
int z13 = tmp6 + tmp5; // Phase 6 int z13 = tmp6 + tmp5; // Phase 6
int z10 = tmp6 - tmp5; int z10 = tmp6 - tmp5;
@ -412,18 +406,14 @@
tmp5 = tmp11 - tmp6; tmp5 = tmp11 - tmp6;
tmp4 = tmp10 - tmp5; tmp4 = tmp10 - tmp5;
computationBufferSpan[workspaceIndex] = (short)(tmp0 + tmp7); computationBufferSpan[col] = (short)(tmp0 + tmp7);
computationBufferSpan[workspaceIndex + 56] = (short)(tmp0 - tmp7); computationBufferSpan[col + 56] = (short)(tmp0 - tmp7);
computationBufferSpan[workspaceIndex + 8] = (short)(tmp1 + tmp6); computationBufferSpan[col + 8] = (short)(tmp1 + tmp6);
computationBufferSpan[workspaceIndex + 48] = (short)(tmp1 - tmp6); computationBufferSpan[col + 48] = (short)(tmp1 - tmp6);
computationBufferSpan[workspaceIndex + 16] = (short)(tmp2 + tmp5); computationBufferSpan[col + 16] = (short)(tmp2 + tmp5);
computationBufferSpan[workspaceIndex + 40] = (short)(tmp2 - tmp5); computationBufferSpan[col + 40] = (short)(tmp2 - tmp5);
computationBufferSpan[workspaceIndex + 24] = (short)(tmp3 + tmp4); computationBufferSpan[col + 24] = (short)(tmp3 + tmp4);
computationBufferSpan[workspaceIndex + 32] = (short)(tmp3 - tmp4); computationBufferSpan[col + 32] = (short)(tmp3 - tmp4);
coefBlockIndex++;
quantTableIndex++;
workspaceIndex++;
} }
// Pass 2: process rows from work array, store into output array. // Pass 2: process rows from work array, store into output array.
@ -464,7 +454,7 @@
int tmp11 = z5 - p4; int tmp11 = z5 - p4;
int tmp13 = p2 + p6; int tmp13 = p2 + p6;
int tmp12 = Multiply(p2 - p6, FIX_1_414213562) - tmp13; /* 2*c4 */ int tmp12 = Multiply(p2 - p6, FIX_1_414213562) - tmp13; // 2*c4
int tmp0 = tmp10 + tmp13; int tmp0 = tmp10 + tmp13;
int tmp3 = tmp10 - tmp13; int tmp3 = tmp10 - tmp13;

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