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LibGfx/ILBMLoader: Add HAM6/HAM8 support

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Nicolas Ramz 2023-09-13 12:17:58 +02:00 • committed by Andrew Kaster
parent 4699c81fc1
commit 8d68f94282
3 changed files with 67 additions and 6 deletions
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62
Userland/Libraries/LibGfx/ImageFormats/ILBMLoader.cpp
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@ -8,6 +8,7 @@
#include <AK/Debug.h>
#include <AK/Endian.h>
#include <AK/FixedArray.h>
#include <AK/IntegralMath.h>
#include <LibGfx/FourCC.h>
#include <LibGfx/ImageFormats/ILBMLoader.h>
@ -89,6 +90,9 @@ struct ILBMLoadingContext {
Vector<Color> color_table;
// number of bits needed to describe current palette
u8 cmap_bits;
RefPtr<Gfx::Bitmap> bitmap;
BMHDHeader bm_header;
@ -132,9 +136,32 @@ static ErrorOr<RefPtr<Gfx::Bitmap>> chunky_to_bitmap(ILBMLoadingContext& context
dbgln_if(ILBM_DEBUG, "created Bitmap {}x{}", width, height);
for (int row = 0; row < height; ++row) {
// Keep color: in HAM mode, current color
// may be based on previous color instead of coming from
// the palette.
Color color = Color::Black;
for (int col = 0; col < width; ++col) {
u8 index = chunky[(width * row) + col];
bitmap->set_pixel(col, row, context.color_table[index]);
if (index < context.color_table.size()) {
color = context.color_table[index];
} else if (has_flag(context.viewport_mode, ViewportMode::HAM)) {
// Get the control bit which will tell use how current pixel should be calculated
u8 control = (index >> context.cmap_bits) & 0x3;
// Since we only have (cmap_bits - 2) bits to define the component,
// we need to pad it to 8 bits.
u8 component = (index % context.color_table.size()) << (8 - context.cmap_bits);
if (control == 1) {
color.set_blue(component);
} else if (control == 2) {
color.set_red(component);
} else {
color.set_green(component);
}
} else {
return Error::from_string_literal("Color map index out of bounds but HAM bit not set");
}
bitmap->set_pixel(col, row, color);
}
}
@ -237,6 +264,26 @@ static ErrorOr<void> extend_ehb_palette(ILBMLoadingContext& context)
return {};
}
static ErrorOr<void> reduce_ham_palette(ILBMLoadingContext& context)
{
u8 bits = context.cmap_bits;
dbgln_if(ILBM_DEBUG, "reduce palette planes={} bits={}", context.bm_header.planes, context.cmap_bits);
if (bits > context.bm_header.planes) {
dbgln_if(ILBM_DEBUG, "need to reduce palette");
bits -= (bits - context.bm_header.planes) + 2;
// bits shouldn't theorically be less than 4 bits in HAM mode.
if (bits < 4)
return Error::from_string_literal("Error while reducing CMAP for HAM: bits too small");
context.color_table.resize((context.color_table.size() >> bits));
context.cmap_bits = bits;
}
return {};
}
static ErrorOr<void> decode_body_chunk(Chunk body_chunk, ILBMLoadingContext& context)
{
dbgln_if(ILBM_DEBUG, "decode_body_chunk {}", body_chunk.data.size());
@ -250,12 +297,14 @@ static ErrorOr<void> decode_body_chunk(Chunk body_chunk, ILBMLoadingContext& con
pixel_data = TRY(planar_to_chunky(body_chunk.data, context));
}
// Some files already have 64 colours defined in the palette,
// maybe for upward compatibility with 256 colours software/hardware.
// DPaint 4 & previous files only have 32 colours so the
// Some files already have 64 colors defined in the palette,
// maybe for upward compatibility with 256 colors software/hardware.
// DPaint 4 & previous files only have 32 colors so the
// palette needs to be extended only for these files.
if (has_flag(context.viewport_mode, ViewportMode::EHB) && context.color_table.size() < 64) {
TRY(extend_ehb_palette(context));
} else if (has_flag(context.viewport_mode, ViewportMode::HAM)) {
TRY(reduce_ham_palette(context));
}
context.bitmap = TRY(chunky_to_bitmap(context, pixel_data));
@ -303,10 +352,11 @@ static ErrorOr<void> decode_iff_chunks(ILBMLoadingContext& context)
while (!chunks.is_empty()) {
auto chunk = TRY(decode_iff_advance_chunk(chunks));
if (chunk.type == FourCC("CMAP")) {
if (chunk.data.size() != (1ul << context.bm_header.planes) * 3)
return Error::from_string_literal("Invalid CMAP chunk size");
// Some files (HAM mainly) have CMAP chunks larger than the planes they advertise: I'm not sure
// why but we should not return an error in this case.
context.color_table = TRY(decode_cmap_chunk(chunk));
context.cmap_bits = AK::ceil_log2(context.color_table.size());
} else if (chunk.type == FourCC("BODY")) {
if (context.color_table.is_empty())
return Error::from_string_literal("Decoding BODY chunk without a color map is not currently supported");