Small updates to JPEG loader

- Remove some unnecessary nesting
- Add frame type (SOF0, et al) to metadata if `.return_metadata` is used

core/image/common.odin

@@ -642,22 +642,23 @@ JFXX_Extension_Code :: enum u8 {
 }
 
 JPEG_Marker :: enum u8 {
-	SOF0  = 0xC0,
+	SOF0  = 0xC0, // Baseline sequential DCT
-	SOF1  = 0xC1,
+	SOF1  = 0xC1, // Extended sequential DCT
-	SOF2  = 0xC2,
+	SOF2  = 0xC2, // Progressive DCT
-	SOF3  = 0xC3,
+	SOF3  = 0xC3, // Lossless (sequential)
+	SOF5  = 0xC5, // Differential sequential DCT
+	SOF6  = 0xC6, // Differential progressive DCT
+	SOF7  = 0xC7, // Differential lossless (sequential)
+	SOF9  = 0xC9, // Extended sequential DCT, Arithmetic coding
+	SOF10 = 0xCA, // Progressive DCT, Arithmetic coding
+	SOF11 = 0xCB, // Lossless (sequential), Arithmetic coding
+	SOF13 = 0xCD, // Differential sequential DCT, Arithmetic coding
+	SOF14 = 0xCE, // Differential progressive DCT, Arithmetic coding
+	SOF15 = 0xCF, // Differential lossless (sequential), Arithmetic coding
+
 	DHT   = 0xC4,
-	SOF5  = 0xC5,
-	SOF6  = 0xC6,
-	SOF7  = 0xC7,
 	JPG   = 0xC8,
-	SOF9  = 0xC9,
-	SOF10 = 0xCA,
-	SOF11 = 0xCB,
 	DAC   = 0xCC,
-	SOF13 = 0xCD,
-	SOF14 = 0xCE,
-	SOF15 = 0xCF,
 	RST0  = 0xD0,
 	RST1  = 0xD1,
 	RST2  = 0xD2,
@@ -713,6 +714,7 @@ JPEG_Info :: struct {
 	jfxx_app0: Maybe(JFXX_APP0),
 	comments: [dynamic]string,
 	exif: [dynamic]Exif,
+	frame_type: JPEG_Marker,
 }
 
 // Function to help with image buffer calculations

core/image/jpeg/jpeg.odin

@@ -219,8 +219,10 @@ load_from_context :: proc(ctx: ^$C, options := Options{}, allocator := context.a
 	defer delete(blocks)
 
 	loop: for {
+		// Loop until we find 0xFF.
 		first = compress.read_u8(ctx) or_return
-		if first == 0xFF {
+		(first == 0xFF) or_continue
+
 		marker := cast(image.JPEG_Marker)compress.read_u8(ctx) or_return
 		if expect_EOI && marker != .EOI {
 			return img, .Extra_Data_After_SOS
@@ -582,6 +584,11 @@ load_from_context :: proc(ctx: ^$C, options := Options{}, allocator := context.a
 				return img, .Invalid_Number_Of_Channels
 			}
 
+			if img.metadata != nil {
+				info := img.metadata.(^image.JPEG_Info)
+				info.frame_type = marker
+			}
+
 			mcu_width = (img.width + 7) / BLOCK_SIZE
 			mcu_height = (img.height + 7) / BLOCK_SIZE
 			block_width = mcu_width
@@ -661,6 +668,10 @@ load_from_context :: proc(ctx: ^$C, options := Options{}, allocator := context.a
 		case .SOF14: // Differential progressive DCT, Arithmetic coding
 			fallthrough
 		case .SOF15: // Differential lossless (sequential), Arithmetic coding
+			if img.metadata != nil {
+				info := img.metadata.(^image.JPEG_Info)
+				info.frame_type = marker
+			}
 			return img, .Unsupported_Frame_Type
 		case .SOS:
 			if img.channels == 0 && img.depth == 0 && img.width == 0 && img.height == 0 {
@@ -1055,7 +1066,6 @@ load_from_context :: proc(ctx: ^$C, options := Options{}, allocator := context.a
 			compress.read_slice_from_memory(ctx, cast(int)length) or_return
 		}
 	}
-	}
 
 	return
 }