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LibGfx: Handle tga images with top-left and bottom-left orientation

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GIMP allows a user to export a TGA image with either of these possible
orientations, so we can easily support it by looking at the X origin and
Y origin values to determine where to put the pixels in the bitmap.
This commit is contained in:
Liav A 2022-12-19 10:48:17 +02:00 • committed by Jelle Raaijmakers
parent 761b89c28e
commit a46df41265
1 changed files with 23 additions and 1 deletions
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24
Userland/Libraries/LibGfx/TGALoader.cpp
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@ -222,6 +222,8 @@ ErrorOr<ImageFrameDescriptor> TGAImageDecoderPlugin::frame(size_t index)
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;
if (index != 0)
return Error::from_string_literal("TGAImageDecoderPlugin: frame index must be 0");
@ -242,12 +244,32 @@ ErrorOr<ImageFrameDescriptor> TGAImageDecoderPlugin::frame(size_t index)
// FIXME: Implement other TGA bit depths
return Error::from_string_literal("TGAImageDecoderPlugin: Can only handle 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");
switch (data_type) {
case TGADataType::UncompressedRGB: {
for (int row = 0; row < height; ++row) {
for (int col = 0; col < width; ++col) {
auto pixel = m_context->reader->read_pixel(bits_per_pixel);
m_context->bitmap->scanline(row)[col] = pixel.data;
auto actual_row = row;
if (y_origin < height)
actual_row = height - 1 - row;
auto actual_col = col;
if (x_origin > width)
actual_col = width - 1 - col;
m_context->bitmap->scanline(actual_row)[actual_col] = pixel.data;
}
}
break;