Pica: Fix A4, IA4 and IA8 texture formats.

Both IA4 and IA8 had their component order mixed up. Additionally, IA4 used the wrong number of nibbles per texel. A4 skipped every second texel.

src/video_core/debug_utils/debug_utils.cpp

@@ -389,13 +389,11 @@ const Math::Vec4<u8> LookupTexture(const u8* source, int x, int y, const Texture
     {
         const u8* source_ptr = source + offset * 2;
 
-        // TODO: component order not verified
-
         if (disable_alpha) {
             // Show intensity as red, alpha as green
-            return { source_ptr[0], source_ptr[1], 0, 255 };
+            return { source_ptr[1], source_ptr[0], 0, 255 };
         } else {
-            return { source_ptr[0], source_ptr[0], source_ptr[0], source_ptr[1]};
+            return { source_ptr[1], source_ptr[1], source_ptr[1], source_ptr[0]};
         }
     }
 
@@ -418,12 +416,10 @@ const Math::Vec4<u8> LookupTexture(const u8* source, int x, int y, const Texture
 
     case Regs::TextureFormat::IA4:
     {
-        const u8* source_ptr = source + offset / 2;
-
-        // TODO: component order not verified
+        const u8* source_ptr = source + offset;
 
-        u8 i = (*source_ptr) & 0xF;
-        u8 a = ((*source_ptr) & 0xF0) >> 4;
+        u8 i = ((*source_ptr) & 0xF0) >> 4;
+        u8 a = (*source_ptr) & 0xF;
         a |= a << 4;
         i |= i << 4;
 
@@ -439,15 +435,13 @@ const Math::Vec4<u8> LookupTexture(const u8* source, int x, int y, const Texture
     {
         const u8* source_ptr = source + offset / 2;
 
-        // TODO: component order not verified
-
         u8 a = (coarse_x % 2) ? ((*source_ptr)&0xF) : (((*source_ptr) & 0xF0) >> 4);
         a |= a << 4;
 
         if (disable_alpha) {
-            return { *source_ptr, *source_ptr, *source_ptr, 255 };
+            return { a, a, a, 255 };
         } else {
-            return { 0, 0, 0, *source_ptr };
+            return { 0, 0, 0, a };
         }
     }