LibGfx/JPEG: Support for images with four components

This patch adds support for properly read images with four components,
basically CMYK or YCCK. However, we still lack color spaces
transformations for this type of image. So, it just postpones failure.

Userland/Libraries/LibGfx/ImageFormats/JPEGLoader.cpp

@@ -115,6 +115,8 @@ struct Macroblock {
         i32 cr[64] = { 0 };
         i32 b[64];
     };
+
+    i32 k[64] = { 0 };
 };
 
 struct MacroblockMeta {
@@ -197,7 +199,7 @@ struct ICCMultiChunkState {
 
 struct Scan {
     // B.2.3 - Scan header syntax
-    Vector<ScanComponent, 3> components;
+    Vector<ScanComponent, 4> components;
 
     u8 spectral_selection_start {};      // Ss
     u8 spectral_selection_end {};        // Se
@@ -242,12 +244,12 @@ struct JPEGLoadingContext {
 
     Scan current_scan;
 
-    Vector<Component, 3> components;
+    Vector<Component, 4> components;
     RefPtr<Gfx::Bitmap> bitmap;
     u16 dc_restart_interval { 0 };
     HashMap<u8, HuffmanTableSpec> dc_tables;
     HashMap<u8, HuffmanTableSpec> ac_tables;
-    Array<i32, 3> previous_dc_values {};
+    Array<i32, 4> previous_dc_values {};
     MacroblockMeta mblock_meta;
     OwnPtr<FixedMemoryStream> stream;
 
@@ -316,8 +318,12 @@ static inline i32* get_component(Macroblock& block, unsigned component)
         return block.y;
     case 1:
         return block.cb;
-    default:
+    case 2:
         return block.cr;
+    case 3:
+        return block.k;
+    default:
+        VERIFY_NOT_REACHED();
     }
 }
 
@@ -1020,7 +1026,7 @@ static ErrorOr<void> read_start_of_frame(Stream& stream, JPEGLoadingContext& con
     set_macroblock_metadata(context);
 
     auto component_count = TRY(stream.read_value<u8>());
-    if (component_count != 1 && component_count != 3) {
+    if (component_count != 1 && component_count != 3 && component_count != 4) {
         dbgln_if(JPEG_DEBUG, "Unsupported number of components in SOF: {}!", component_count);
         return Error::from_string_literal("Unsupported number of components in SOF");
     }