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JimBobSquarePantsJimBobSquarePants
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Merge pull request #546 from SixLabors/js/projective-transforms
Add Projective Transforms
2 parents 6b4de97 + 775aa90 commit 3cc7caa

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8 files changed

+380
-63
lines changed

8 files changed

+380
-63
lines changed

‎src/ImageSharp/Processing/Transforms/Processors/AffineTransformProcessor.cs‎

Lines changed: 12 additions & 10 deletions
Original file line numberDiff line numberDiff line change
@@ -5,6 +5,8 @@
55
using System.Collections.Generic;
66
using System.Linq;
77
using System.Numerics;
8+
using System.Runtime.CompilerServices;
9+
using System.Runtime.InteropServices;
810
using System.Threading.Tasks;
911
using SixLabors.ImageSharp.Advanced;
1012
using SixLabors.ImageSharp.Memory;
@@ -120,9 +122,9 @@ protected override void OnFrameApply(
120122
configuration.ParallelOptions,
121123
y =>
122124
{
123-
Span<TPixel> destRow = destination.GetPixelRowSpan(y);
124-
Span<float> ySpan = yBuffer.GetRowSpan(y);
125-
Span<float> xSpan = xBuffer.GetRowSpan(y);
125+
ref TPixel destRowRef = ref MemoryMarshal.GetReference(destination.GetPixelRowSpan(y));
126+
ref float ySpanRef = ref MemoryMarshal.GetReference(yBuffer.GetRowSpan(y));
127+
ref float xSpanRef = ref MemoryMarshal.GetReference(xBuffer.GetRowSpan(y));
126128

127129
for (int x = 0; x < width; x++)
128130
{
@@ -164,24 +166,24 @@ protected override void OnFrameApply(
164166
// I've optimized where I can but am always open to suggestions.
165167
if (yScale > 1 && xScale > 1)
166168
{
167-
CalculateWeightsDown(top, bottom, minY, maxY, point.Y, sampler, yScale, ySpan);
168-
CalculateWeightsDown(left, right, minX, maxX, point.X, sampler, xScale, xSpan);
169+
CalculateWeightsDown(top, bottom, minY, maxY, point.Y, sampler, yScale, ref ySpanRef, yLength);
170+
CalculateWeightsDown(left, right, minX, maxX, point.X, sampler, xScale, ref xSpanRef, xLength);
169171
}
170172
else
171173
{
172-
CalculateWeightsScaleUp(minY, maxY, point.Y, sampler, ySpan);
173-
CalculateWeightsScaleUp(minX, maxX, point.X, sampler, xSpan);
174+
CalculateWeightsScaleUp(minY, maxY, point.Y, sampler, ref ySpanRef);
175+
CalculateWeightsScaleUp(minX, maxX, point.X, sampler, ref xSpanRef);
174176
}
175177

176178
// Now multiply the results against the offsets
177179
Vector4 sum = Vector4.Zero;
178180
for (int yy = 0, j = minY; j <= maxY; j++, yy++)
179181
{
180-
float yWeight = ySpan[yy];
182+
float yWeight = Unsafe.Add(ref ySpanRef, yy);
181183

182184
for (int xx = 0, i = minX; i <= maxX; i++, xx++)
183185
{
184-
float xWeight = xSpan[xx];
186+
float xWeight = Unsafe.Add(ref xSpanRef, xx);
185187
var vector = source[i, j].ToVector4();
186188

187189
// Values are first premultiplied to prevent darkening of edge pixels
@@ -190,7 +192,7 @@ protected override void OnFrameApply(
190192
}
191193
}
192194

193-
ref TPixel dest = ref destRow[x];
195+
ref TPixel dest = ref Unsafe.Add(ref destRowRef, x);
194196

195197
// Reverse the premultiplication
196198
dest.PackFromVector4(sum.UnPremultiply());

‎src/ImageSharp/Processing/Transforms/Processors/InterpolatedTransformProcessorBase.cs‎

Lines changed: 9 additions & 10 deletions
Original file line numberDiff line numberDiff line change
@@ -42,12 +42,12 @@ protected InterpolatedTransformProcessorBase(IResampler sampler)
4242
/// <param name="point">The transformed point dimension</param>
4343
/// <param name="sampler">The sampler</param>
4444
/// <param name="scale">The transformed image scale relative to the source</param>
45-
/// <param name="weights">The collection of weights</param>
45+
/// <param name="weightsRef">The reference to the collection of weights</param>
46+
/// <param name="length">The length of the weights collection</param>
4647
[MethodImpl(MethodImplOptions.AggressiveInlining)]
47-
protected static void CalculateWeightsDown(int min, int max, int sourceMin, int sourceMax, float point, IResampler sampler, float scale, Span<float> weights)
48+
protected static void CalculateWeightsDown(int min, int max, int sourceMin, int sourceMax, float point, IResampler sampler, float scale, ref float weightsRef, int length)
4849
{
4950
float sum = 0;
50-
ref float weightsBaseRef = ref weights[0];
5151

5252
// Downsampling weights requires more edge sampling plus normalization of the weights
5353
for (int x = 0, i = min; i <= max; i++, x++)
@@ -65,14 +65,14 @@ protected static void CalculateWeightsDown(int min, int max, int sourceMin, int
6565

6666
float weight = sampler.GetValue((index - point) / scale);
6767
sum += weight;
68-
Unsafe.Add(ref weightsBaseRef, x) = weight;
68+
Unsafe.Add(ref weightsRef, x) = weight;
6969
}
7070

7171
if (sum > 0)
7272
{
73-
for (int i = 0; i < weights.Length; i++)
73+
for (int i = 0; i < length; i++)
7474
{
75-
ref float wRef = ref Unsafe.Add(ref weightsBaseRef, i);
75+
ref float wRef = ref Unsafe.Add(ref weightsRef, i);
7676
wRef = wRef / sum;
7777
}
7878
}
@@ -85,15 +85,14 @@ protected static void CalculateWeightsDown(int min, int max, int sourceMin, int
8585
/// <param name="sourceMax">The maximum source bounds</param>
8686
/// <param name="point">The transformed point dimension</param>
8787
/// <param name="sampler">The sampler</param>
88-
/// <param name="weights">The collection of weights</param>
88+
/// <param name="weightsRef">The reference to the collection of weights</param>
8989
[MethodImpl(MethodImplOptions.AggressiveInlining)]
90-
protected static void CalculateWeightsScaleUp(int sourceMin, int sourceMax, float point, IResampler sampler, Span<float> weights)
90+
protected static void CalculateWeightsScaleUp(int sourceMin, int sourceMax, float point, IResampler sampler, ref float weightsRef)
9191
{
92-
ref float weightsBaseRef = ref weights[0];
9392
for (int x = 0, i = sourceMin; i <= sourceMax; i++, x++)
9493
{
9594
float weight = sampler.GetValue(i - point);
96-
Unsafe.Add(ref weightsBaseRef, x) = weight;
95+
Unsafe.Add(ref weightsRef, x) = weight;
9796
}
9897
}
9998

‎src/ImageSharp/Processing/Transforms/Processors/ProjectiveTransformProcessor.cs‎

Lines changed: 32 additions & 17 deletions
Original file line numberDiff line numberDiff line change
@@ -5,6 +5,8 @@
55
using System.Collections.Generic;
66
using System.Linq;
77
using System.Numerics;
8+
using System.Runtime.CompilerServices;
9+
using System.Runtime.InteropServices;
810
using System.Threading.Tasks;
911
using SixLabors.ImageSharp.Advanced;
1012
using SixLabors.ImageSharp.Memory;
@@ -70,6 +72,7 @@ protected override void OnFrameApply(ImageFrame<TPixel> source, ImageFrame<TPixe
7072

7173
// Convert from screen to world space.
7274
Matrix4x4.Invert(matrix, out matrix);
75+
const float Epsilon = 0.0000001F;
7376

7477
if (this.Sampler is NearestNeighborResampler)
7578
{
@@ -83,10 +86,15 @@ protected override void OnFrameApply(ImageFrame<TPixel> source, ImageFrame<TPixe
8386

8487
for (int x = 0; x < width; x++)
8588
{
86-
var point = Point.Round(Vector2.Transform(new Vector2(x, y), matrix));
87-
if (sourceBounds.Contains(point.X, point.Y))
89+
var v3 = Vector3.Transform(new Vector3(x, y, 1), matrix);
90+
91+
float z = MathF.Max(v3.Z, Epsilon);
92+
int px = (int)MathF.Round(v3.X / z);
93+
int py = (int)MathF.Round(v3.Y / z);
94+
95+
if (sourceBounds.Contains(px, py))
8896
{
89-
destRow[x] = source[point.X, point.Y];
97+
destRow[x] = source[px, py];
9098
}
9199
}
92100
});
@@ -100,7 +108,10 @@ protected override void OnFrameApply(ImageFrame<TPixel> source, ImageFrame<TPixe
100108
(float radius, float scale, float ratio) yRadiusScale = this.GetSamplingRadius(source.Height, destination.Height);
101109
float xScale = xRadiusScale.scale;
102110
float yScale = yRadiusScale.scale;
103-
var radius = new Vector2(xRadiusScale.radius, yRadiusScale.radius);
111+
112+
// Using Vector4 with dummy 0-s, because Vector2 SIMD implementation is not reliable:
113+
var radius = new Vector4(xRadiusScale.radius, yRadiusScale.radius, 0, 0);
114+
104115
IResampler sampler = this.Sampler;
105116
var maxSource = new Vector4(maxSourceX, maxSourceY, maxSourceX, maxSourceY);
106117
int xLength = (int)MathF.Ceiling((radius.X * 2) + 2);
@@ -117,19 +128,23 @@ protected override void OnFrameApply(ImageFrame<TPixel> source, ImageFrame<TPixe
117128
configuration.ParallelOptions,
118129
y =>
119130
{
120-
Span<TPixel> destRow = destination.GetPixelRowSpan(y);
121-
Span<float> ySpan = yBuffer.GetRowSpan(y);
122-
Span<float> xSpan = xBuffer.GetRowSpan(y);
131+
ref TPixel destRowRef = ref MemoryMarshal.GetReference(destination.GetPixelRowSpan(y));
132+
ref float ySpanRef = ref MemoryMarshal.GetReference(yBuffer.GetRowSpan(y));
133+
ref float xSpanRef = ref MemoryMarshal.GetReference(xBuffer.GetRowSpan(y));
123134

124135
for (int x = 0; x < width; x++)
125136
{
126137
// Use the single precision position to calculate correct bounding pixels
127138
// otherwise we get rogue pixels outside of the bounds.
128-
var point = Vector2.Transform(new Vector2(x, y), matrix);
139+
var v3 = Vector3.Transform(new Vector3(x, y, 1), matrix);
140+
float z = MathF.Max(v3.Z, Epsilon);
141+
142+
// Using Vector4 with dummy 0-s, because Vector2 SIMD implementation is not reliable:
143+
Vector4 point = new Vector4(v3.X, v3.Y, 0, 0) / z;
129144

130145
// Clamp sampling pixel radial extents to the source image edges
131-
Vector2 maxXY = point + radius;
132-
Vector2 minXY = point - radius;
146+
Vector4 maxXY = point + radius;
147+
Vector4 minXY = point - radius;
133148

134149
// max, maxY, minX, minY
135150
var extents = new Vector4(
@@ -161,24 +176,24 @@ protected override void OnFrameApply(ImageFrame<TPixel> source, ImageFrame<TPixe
161176
// I've optimized where I can but am always open to suggestions.
162177
if (yScale > 1 && xScale > 1)
163178
{
164-
CalculateWeightsDown(top, bottom, minY, maxY, point.Y, sampler, yScale, ySpan);
165-
CalculateWeightsDown(left, right, minX, maxX, point.X, sampler, xScale, xSpan);
179+
CalculateWeightsDown(top, bottom, minY, maxY, point.Y, sampler, yScale, ref ySpanRef, yLength);
180+
CalculateWeightsDown(left, right, minX, maxX, point.X, sampler, xScale, ref xSpanRef, xLength);
166181
}
167182
else
168183
{
169-
CalculateWeightsScaleUp(minY, maxY, point.Y, sampler, ySpan);
170-
CalculateWeightsScaleUp(minX, maxX, point.X, sampler, xSpan);
184+
CalculateWeightsScaleUp(minY, maxY, point.Y, sampler, ref ySpanRef);
185+
CalculateWeightsScaleUp(minX, maxX, point.X, sampler, ref xSpanRef);
171186
}
172187

173188
// Now multiply the results against the offsets
174189
Vector4 sum = Vector4.Zero;
175190
for (int yy = 0, j = minY; j <= maxY; j++, yy++)
176191
{
177-
float yWeight = ySpan[yy];
192+
float yWeight = Unsafe.Add(ref ySpanRef, yy);
178193

179194
for (int xx = 0, i = minX; i <= maxX; i++, xx++)
180195
{
181-
float xWeight = xSpan[xx];
196+
float xWeight = Unsafe.Add(ref xSpanRef, xx);
182197
var vector = source[i, j].ToVector4();
183198

184199
// Values are first premultiplied to prevent darkening of edge pixels
@@ -187,7 +202,7 @@ protected override void OnFrameApply(ImageFrame<TPixel> source, ImageFrame<TPixe
187202
}
188203
}
189204

190-
ref TPixel dest = ref destRow[x];
205+
ref TPixel dest = ref Unsafe.Add(ref destRowRef, x);
191206

192207
// Reverse the premultiplication
193208
dest.PackFromVector4(sum.UnPremultiply());

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