LibGfx: Respect order of image data in TGAImageDecoderPlugin

Previously, the order of data was incorrectly based on x_origin and
y_origin, which are meant for where on the screen the image should be
placed (TarGA is an image format meant for graphic cards), instead of
Image descriptor bits 4 and 5, which specify the direction.

This fixes a problem where tga files generated with magick would render
up-side-down.

The test images where created in GIMP, 4 simple 2x2 images
exported as .tga, no compression, origin: Bottom Left

square-bottom-left.tga:
Red, Green
Blue, Magenta

square-bottom-right.tga:
Green, Red
Magenta, Blue

square-top-left.tga:
Blue, Magenta
Red, Green

square-top-right.tga:
Magenta, Blue
Green, Red

then this script was ran:
```python
def update_tga_descriptor(file_path, top_to_bottom, left_to_right):
    with open(file_path, 'r+b') as f:
        header = f.read(18)
        descriptor = header[17]

        descriptor &= ~(1 << 4);
        descriptor &= ~(1 << 5);

        if left_to_right:
            descriptor |= 1 << 4;

        if top_to_bottom:
            descriptor |= 1 << 5;

        header = header[:17] + bytes([descriptor])
        f.seek(0)
        f.write(header)

update_tga_descriptor('square-bottom-left.tga', False, False)
update_tga_descriptor('square-bottom-right.tga', False, True)
update_tga_descriptor('square-top-left.tga', True, False)
update_tga_descriptor('square-top-right.tga', True, True)
```

Tests/LibGfx/TestImageDecoder.cpp

@@ -850,6 +850,29 @@ TEST_CASE(test_targa_black_and_white_uncompressed)
     TRY_OR_FAIL(expect_single_frame(*plugin_decoder));
 }
 
+TEST_CASE(test_targa_image_descriptor)
+{
+    Array test_inputs = {
+        TEST_INPUT("tga/square-bottom-left.tga"sv),
+        TEST_INPUT("tga/square-bottom-right.tga"sv),
+        TEST_INPUT("tga/square-top-left.tga"sv),
+        TEST_INPUT("tga/square-top-right.tga"sv),
+    };
+
+    for (auto test_input : test_inputs) {
+        auto file = TRY_OR_FAIL(Core::MappedFile::map(test_input));
+        EXPECT(Gfx::TGAImageDecoderPlugin::validate_before_create(file->bytes()));
+        auto plugin_decoder = TRY_OR_FAIL(Gfx::TGAImageDecoderPlugin::create(file->bytes()));
+
+        auto frame = TRY_OR_FAIL(expect_single_frame_of_size(*plugin_decoder, { 2, 2 }));
+
+        EXPECT_EQ(frame.image->get_pixel(0, 0), Gfx::Color::NamedColor::Red);
+        EXPECT_EQ(frame.image->get_pixel(1, 0), Gfx::Color::NamedColor::Green);
+        EXPECT_EQ(frame.image->get_pixel(0, 1), Gfx::Color::NamedColor::Blue);
+        EXPECT_EQ(frame.image->get_pixel(1, 1), Gfx::Color::NamedColor::Magenta);
+    }
+}
+
 TEST_CASE(test_tiff_uncompressed)
 {
     auto file = TRY_OR_FAIL(Core::MappedFile::map(TEST_INPUT("tiff/uncompressed.tiff"sv)));

Userland/Libraries/LibGfx/ImageFormats/TGALoader.cpp

@@ -150,8 +150,7 @@ ErrorOr<ImageFrameDescriptor> TGAImageDecoderPlugin::frame(size_t index, Optiona
     auto data_type = m_context->header.data_type_code;
     auto width = m_context->header.width;
     auto height = m_context->header.height;
-    auto x_origin = m_context->header.x_origin;
-    auto y_origin = m_context->header.y_origin;
+    auto image_descriptior = m_context->header.image_descriptor;
 
     if (index != 0)
         return Error::from_string_literal("TGAImageDecoderPlugin: frame index must be 0");
@@ -178,18 +177,8 @@ ErrorOr<ImageFrameDescriptor> TGAImageDecoderPlugin::frame(size_t index, Optiona
         return Error::from_string_literal("TGAImageDecoderPlugin: Can only handle 8, 24 and 32 bits per pixel");
     }
 
-    // FIXME: Try to understand the Image origin (instead of X and Y origin coordinates)
-    // based on the Image descriptor, Field 5.6, bits 4 and 5.
-
-    // NOTE: If Y origin is set to a negative number, just assume the generating software
-    // meant that we start with Y origin at the top height of the picture.
-    // At least this is the observed behavior when generating some pictures in GIMP.
-    if (y_origin < 0)
-        y_origin = height;
-    if (y_origin != 0 && y_origin != height)
-        return Error::from_string_literal("TGAImageDecoderPlugin: Can only handle Y origin which is 0 or the entire height");
-    if (x_origin != 0 && x_origin != width)
-        return Error::from_string_literal("TGAImageDecoderPlugin: Can only handle X origin which is 0 or the entire width");
+    auto is_top_to_bottom = (image_descriptior & 1 << 5) == 0;
+    auto is_left_to_right = (image_descriptior & 1 << 4) == 0;
 
     VERIFY((bits_per_pixel % 8) == 0);
     auto bytes_per_pixel = bits_per_pixel / 8;
@@ -200,10 +189,10 @@ ErrorOr<ImageFrameDescriptor> TGAImageDecoderPlugin::frame(size_t index, Optiona
         for (int row = 0; row < height; ++row) {
             for (int col = 0; col < width; ++col) {
                 auto actual_row = row;
-                if (y_origin < height)
+                if (is_top_to_bottom)
                     actual_row = height - 1 - row;
                 auto actual_col = col;
-                if (x_origin > width)
+                if (!is_left_to_right)
                     actual_col = width - 1 - col;
                 bitmap->scanline(actual_row)[actual_col] = TRY(read_pixel_from_stream(m_context->stream, bytes_per_pixel));
             }
@@ -224,10 +213,10 @@ ErrorOr<ImageFrameDescriptor> TGAImageDecoderPlugin::frame(size_t index, Optiona
                 int row = current_pixel_index / width;
                 int col = current_pixel_index % width;
                 auto actual_row = row;
-                if (y_origin < height)
+                if (is_top_to_bottom)
                     actual_row = height - 1 - row;
                 auto actual_col = col;
-                if (x_origin > width)
+                if (!is_left_to_right)
                     actual_col = width - 1 - col;
                 bitmap->scanline(actual_row)[actual_col] = pixel;
                 if (pixel_packet_header.raw && (current_pixel_index + 1) < max_pixel_index)