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Rewritten defiltering, should work properly now

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Luna 2025-07-13 08:06:39 +02:00
parent 5b4d489b79
commit b8cb54b034
1 changed files with 65 additions and 71 deletions
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136
lily_png.cpp
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@ -1,3 +1,4 @@
#define STB_IMAGE_WRITE_IMPLEMENTATION
#include "lily_png.h"
#include <math.h>
@ -193,13 +194,12 @@ static void read_raw_data(const std::string &file_path, buffer_unsigned &data, m
}
}
template <typename T>
T paeth_predict(T a, T b, T c)
int paeth_predict(int a, int b, int c)
{
T pred = a+b-c;
T pred1 = abs(pred - a);
T pred2 = abs(pred - b);
T pred3 = abs(pred - c);
int pred = a+b-c;
int pred1 = abs(pred - a);
int pred2 = abs(pred - b);
int pred3 = abs(pred - c);
if (pred1 <= pred2 && pred1 <= pred3)
return a;
if (pred2 <= pred3)
@ -207,6 +207,57 @@ T paeth_predict(T a, T b, T c)
return c;
}
static void filter_scanline(unsigned char *scanline, unsigned char *previous_scanline, unsigned char *dest, metadata &meta, unsigned char filter_type)
{
size_t pixel_size = get_pixel_bit_size(meta);
for (int i = 0; i < ceil(pixel_size/8.0f) * meta.width; i++)
{
long index_before = 0;
switch (filter_type)
{
case 0:
dest[i] = scanline[i];
break;
case 1:
if (pixel_size < 8)
index_before = i - 1;
else
index_before = i - ceil(pixel_size/8.0f);
if (index_before <= 0)
dest[i] = scanline[i] + 0;
else
dest[i] = scanline[i] + dest[index_before];
break;
case 2:
dest[i] = scanline[i] + previous_scanline[i];
break;
case 3:
if (pixel_size < 8)
index_before = i - 1;
else
index_before = i - ceil(pixel_size/8.0f);
if (index_before <= 0)
dest[i] = scanline[i] + floor((0 + previous_scanline[i])/2);
else
dest[i] = scanline[i] + floor((dest[index_before] + previous_scanline[i])/2);
break;
case 4:
if (pixel_size < 8)
index_before = i - 1;
else
index_before = i - ceil(pixel_size/8.0f);
if (index_before <= 0)
dest[i] = scanline[i] + paeth_predict(0, previous_scanline[i], 0);
else
dest[i] = scanline[i] + paeth_predict(dest[index_before], previous_scanline[i], previous_scanline[index_before]);
break;
default:
std::println("Non standard filter");
break;
}
}
}
static void filter(buffer_unsigned &data, buffer_unsigned &dest ,metadata &meta)
{
unsigned long index = 0;
@ -214,77 +265,20 @@ static void filter(buffer_unsigned &data, buffer_unsigned &dest ,metadata &meta)
size_t pixel_size = get_pixel_bit_size(meta);
unsigned long scanlines = 0;
dest.allocate(get_uncompressed_size(meta));
unsigned char *previous_scanline = nullptr;
while (scanlines < meta.height)
{
unsigned char filter = 0;
for (int i = 0; i < (pixel_size/8) * meta.width + 1; i++)
{
if (i == 0)
{
filter = data.data[index + i];
continue;
}
long index_before = 0;
long index_before2 = 0;
long index_before3 = 0;
switch (filter)
{
case 0:
dest.data[index_dest] = data.data[index + i];
break;
case 1:
if (pixel_size < 8)
index_before = index + i - 1;
else
index_before = index + i - pixel_size/8;
if (index_before <= 0)
break;
dest.data[index_dest] = data.data[index + i] + dest.data[index_before];
break;
case 2:
index_before = (index + i) - (meta.width * (pixel_size/8));
if (index_before <= 0)
break;
dest.data[index_dest] = data.data[index + i] + dest.data[index_before];
break;
case 3:
if (pixel_size < 8)
index_before = index + i - 1;
else
index_before = index + i - pixel_size/8;
if (index_before <= 0)
break;
index_before2 = (index + i) - (meta.width * (pixel_size/8));
dest.data[index_dest] = data.data[index + i] + floor((dest.data[index_before] + dest.data[index_before2])/2);
break;
case 4:
if (pixel_size < 8)
index_before = index + i - 1;
else
index_before = index + i - pixel_size/8;
if (index_before <= 0)
break;
index_before2 = (index + i) - (meta.width * (pixel_size/8));
index_before3 = 0;
if (pixel_size < 8)
index_before3 = index_before2 + i - 1;
else
index_before3 = index_before2 + i - pixel_size/8;
if (index_before3 <= 0)
break;
dest.data[index_dest] = data.data[index + i] + paeth_predict(dest.data[index_before], dest.data[index_before2], dest.data[index_before3]);
break;
default:
std::println("Non standard filter");
break;
}
index_dest++;
}
index += (pixel_size/8) * meta.width + 1;
unsigned char filter = data.data[index];
std::println("Filter {}", filter);
filter_scanline(&data.data[index++], previous_scanline, &dest.data[index_dest], meta, filter);
previous_scanline = &dest.data[index_dest];
index += ceil(pixel_size/8.0f) * meta.width;
index_dest += ceil(pixel_size/8.0f) * meta.width;
scanlines++;
}
}
void read_png(const std::string &file_path, buffer_unsigned &data)
{
buffer_unsigned tmp_data{};