Move reading frame ComponentIds out of only metadata block

src/ImageSharp/Formats/Jpeg/JpegDecoderCore.cs

@@ -845,57 +845,57 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
 
             this.Frame = new JpegFrame(frameMarker, precision, frameWidth, frameHeight, componentCount);
 
-            if (!metadataOnly)
+            remaining -= length;
+
+            // Validate: remaining part must be equal to components * 3
+            const int componentBytes = 3;
+            if (remaining != componentCount * componentBytes)
             {
-                remaining -= length;
+                JpegThrowHelper.ThrowBadMarker("SOFn", remaining);
+            }
 
-                // Validate: remaining part must be equal to components * 3
-                const int componentBytes = 3;
-                if (remaining != componentCount * componentBytes)
-                {
-                    JpegThrowHelper.ThrowBadMarker("SOFn", remaining);
-                }
+            // components*3 bytes: component data
+            stream.Read(this.temp, 0, remaining);
 
-                // components*3 bytes: component data
-                stream.Read(this.temp, 0, remaining);
+            // No need to pool this. They max out at 4
+            this.Frame.ComponentIds = new byte[componentCount];
+            this.Frame.ComponentOrder = new byte[componentCount];
+            this.Frame.Components = new JpegComponent[componentCount];
 
-                // No need to pool this. They max out at 4
-                this.Frame.ComponentIds = new byte[componentCount];
-                this.Frame.ComponentOrder = new byte[componentCount];
-                this.Frame.Components = new JpegComponent[componentCount];
+            int maxH = 0;
+            int maxV = 0;
+            int index = 0;
+            for (int i = 0; i < componentCount; i++)
+            {
+                byte hv = this.temp[index + 1];
+                int h = (hv >> 4) & 15;
+                int v = hv & 15;
 
-                int maxH = 0;
-                int maxV = 0;
-                int index = 0;
-                for (int i = 0; i < componentCount; i++)
+                if (maxH < h)
                 {
-                    byte hv = this.temp[index + 1];
-                    int h = (hv >> 4) & 15;
-                    int v = hv & 15;
+                    maxH = h;
+                }
 
-                    if (maxH < h)
-                    {
-                        maxH = h;
-                    }
+                if (maxV < v)
+                {
+                    maxV = v;
+                }
 
-                    if (maxV < v)
-                    {
-                        maxV = v;
-                    }
+                var component = new JpegComponent(this.Configuration.MemoryAllocator, this.Frame, this.temp[index], h, v, this.temp[index + 2], i);
 
-                    var component = new JpegComponent(this.Configuration.MemoryAllocator, this.Frame, this.temp[index], h, v, this.temp[index + 2], i);
+                this.Frame.Components[i] = component;
+                this.Frame.ComponentIds[i] = component.Id;
 
-                    this.Frame.Components[i] = component;
-                    this.Frame.ComponentIds[i] = component.Id;
+                index += componentBytes;
+            }
 
-                    index += componentBytes;
-                }
+            this.ColorSpace = this.DeduceJpegColorSpace(componentCount, this.Frame.Components);
 
-                this.ColorSpace = this.DeduceJpegColorSpace(componentCount, this.Frame.Components);
-                this.Metadata.GetJpegMetadata().ColorType = this.ColorSpace == JpegColorSpace.Grayscale ? JpegColorType.Luminance : JpegColorType.YCbCr;
+            this.Metadata.GetJpegMetadata().ColorType = this.ColorSpace == JpegColorSpace.Grayscale ? JpegColorType.Luminance : JpegColorType.YCbCr;
 
+            if (!metadataOnly)
+            {
                 this.Frame.Init(maxH, maxV);
-
                 this.scanDecoder.InjectFrameData(this.Frame, this);
             }
         }