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Adds 16bpp support for BMP File Format #67608

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merged 1 commit into from Apr 13, 2023
Merged

Adds 16bpp support for BMP File Format #67608

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64 changes: 59 additions & 5 deletions modules/bmp/image_loader_bmp.cpp
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Expand Up @@ -32,6 +32,16 @@

#include "core/io/file_access_memory.h"

static uint8_t get_mask_width(uint16_t mask) {
// Returns number of ones in the binary value of the parameter: mask.
// Uses a Simple pop_count.
uint8_t c = 0u;
for (; mask != 0u; mask &= mask - 1u) {
c++;
}
return c;
}

Error ImageLoaderBMP::convert_to_image(Ref<Image> p_image,
const uint8_t *p_buffer,
const uint8_t *p_color_buffer,
Expand Down Expand Up @@ -71,9 +81,6 @@ Error ImageLoaderBMP::convert_to_image(Ref<Image> p_image,
vformat("4-bpp BMP images must have a width that is a multiple of 2, but the imported BMP is %d pixels wide.", int(width)));
ERR_FAIL_COND_V_MSG(height % 2 != 0, ERR_UNAVAILABLE,
vformat("4-bpp BMP images must have a height that is a multiple of 2, but the imported BMP is %d pixels tall.", int(height)));

} else if (bits_per_pixel == 16) {
ERR_FAIL_V_MSG(ERR_UNAVAILABLE, "16-bpp BMP images are not supported.");
}

// Image data (might be indexed)
Expand All @@ -96,7 +103,7 @@ Error ImageLoaderBMP::convert_to_image(Ref<Image> p_image,

// The actual data traversal is determined by
// the data width in case of 8/4/2/1 bit images
const uint32_t w = bits_per_pixel >= 24 ? width : width_bytes;
const uint32_t w = bits_per_pixel >= 16 ? width : width_bytes;
const uint8_t *line = p_buffer + (line_width * (height - 1));
const uint8_t *end_buffer = p_buffer + p_header.bmp_file_header.bmp_file_size - p_header.bmp_file_header.bmp_file_offset;

Expand Down Expand Up @@ -149,6 +156,34 @@ Error ImageLoaderBMP::convert_to_image(Ref<Image> p_image,
index += 1;
line_ptr += 1;
} break;
case 16: {
uint16_t rgb = (static_cast<uint16_t>(line_ptr[1]) << 8) | line_ptr[0];
// A1R5G5B5/X1R5G5B5 => uint16_t
// [A/X]1R5G2 | G3B5 => uint8_t | uint8_t
uint8_t ba = (rgb & p_header.bmp_bitfield.alpha_mask) >> p_header.bmp_bitfield.alpha_offset; // Alpha 0b 1000 ...
uint8_t b0 = (rgb & p_header.bmp_bitfield.red_mask) >> p_header.bmp_bitfield.red_offset; // Red 0b 0111 1100 ...
uint8_t b1 = (rgb & p_header.bmp_bitfield.green_mask) >> p_header.bmp_bitfield.green_offset; // Green 0b 0000 0011 1110 ...
uint8_t b2 = (rgb & p_header.bmp_bitfield.blue_mask); // >> p_header.bmp_bitfield.blue_offset; // Blue 0b ... 0001 1111

// Next we apply some color scaling going from a variable value space to a 256 value space.
// This may be simplified some but left as is for legibility.
// float scaled_value = unscaled_value * byte_max_value / color_channel_maxium_value + rounding_offset;
float f0 = b0 * 255.0f / static_cast<float>(p_header.bmp_bitfield.red_max) + 0.5f;
float f1 = b1 * 255.0f / static_cast<float>(p_header.bmp_bitfield.green_max) + 0.5f;
float f2 = b2 * 255.0f / static_cast<float>(p_header.bmp_bitfield.blue_max) + 0.5f;
write_buffer[index + 0] = static_cast<uint8_t>(f0); // R
write_buffer[index + 1] = static_cast<uint8_t>(f1); // G
write_buffer[index + 2] = static_cast<uint8_t>(f2); // B

if (p_header.bmp_bitfield.alpha_mask_width > 0) {
write_buffer[index + 3] = ba * 0xFF; // Alpha value(Always true or false so no scaling)
} else {
write_buffer[index + 3] = 0xFF; // No Alpha channel, Show everything.
}

index += 4;
line_ptr += 2;
} break;
case 24: {
write_buffer[index + 2] = line_ptr[0];
write_buffer[index + 1] = line_ptr[1];
Expand Down Expand Up @@ -253,13 +288,32 @@ Error ImageLoaderBMP::load_image(Ref<Image> p_image, Ref<FileAccess> f, BitField
bmp_header.bmp_info_header.bmp_important_colors = f->get_32();

switch (bmp_header.bmp_info_header.bmp_compression) {
case BI_BITFIELDS: {
bmp_header.bmp_bitfield.red_mask = f->get_32();
bmp_header.bmp_bitfield.green_mask = f->get_32();
bmp_header.bmp_bitfield.blue_mask = f->get_32();
bmp_header.bmp_bitfield.alpha_mask = f->get_32();

bmp_header.bmp_bitfield.red_mask_width = get_mask_width(bmp_header.bmp_bitfield.red_mask);
bmp_header.bmp_bitfield.green_mask_width = get_mask_width(bmp_header.bmp_bitfield.green_mask);
bmp_header.bmp_bitfield.blue_mask_width = get_mask_width(bmp_header.bmp_bitfield.blue_mask);
bmp_header.bmp_bitfield.alpha_mask_width = get_mask_width(bmp_header.bmp_bitfield.alpha_mask);

bmp_header.bmp_bitfield.alpha_offset = bmp_header.bmp_bitfield.red_mask_width + bmp_header.bmp_bitfield.green_mask_width + bmp_header.bmp_bitfield.blue_mask_width;
bmp_header.bmp_bitfield.red_offset = bmp_header.bmp_bitfield.green_mask_width + bmp_header.bmp_bitfield.blue_mask_width;
bmp_header.bmp_bitfield.green_offset = bmp_header.bmp_bitfield.blue_mask_width;

bmp_header.bmp_bitfield.red_max = (1 << bmp_header.bmp_bitfield.red_mask_width) - 1;
bmp_header.bmp_bitfield.green_max = (1 << bmp_header.bmp_bitfield.green_mask_width) - 1;
bmp_header.bmp_bitfield.blue_max = (1 << bmp_header.bmp_bitfield.blue_mask_width) - 1;
} break;
case BI_RLE8:
case BI_RLE4:
case BI_CMYKRLE8:
case BI_CMYKRLE4: {
// Stop parsing.
ERR_FAIL_V_MSG(ERR_UNAVAILABLE,
vformat("Compressed BMP files are not supported: %s", f->get_path()));
vformat("RLE compressed BMP files are not yet supported: %s", f->get_path()));
} break;
}
// Don't rely on sizeof(bmp_file_header) as structure padding
Expand Down
19 changes: 19 additions & 0 deletions modules/bmp/image_loader_bmp.h
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Expand Up @@ -74,6 +74,25 @@ class ImageLoaderBMP : public ImageFormatLoader {
uint32_t bmp_colors_used = 0;
uint32_t bmp_important_colors = 0;
} bmp_info_header;

struct bmp_bitfield_s {
uint16_t alpha_mask = 0x8000;
uint16_t red_mask = 0x7C00;
uint16_t green_mask = 0x03E0;
uint16_t blue_mask = 0x001F;
uint16_t alpha_mask_width = 1u;
uint16_t red_mask_width = 5u;
uint16_t green_mask_width = 5u;
uint16_t blue_mask_width = 5u;
uint8_t alpha_offset = 15u; // Used for bit shifting.
uint8_t red_offset = 10u; // Used for bit shifting.
uint8_t green_offset = 5u; // Used for bit shifting.
//uint8_t blue_offset = 0u; // Always LSB aligned no shifting needed.
//uint8_t alpha_max = 1u; // Always boolean or on, so no scaling needed.
uint8_t red_max = 32u; // Used for color space scaling.
uint8_t green_max = 32u; // Used for color space scaling.
uint8_t blue_max = 32u; // Used for color space scaling.
} bmp_bitfield;
};

static Error convert_to_image(Ref<Image> p_image,
Expand Down