lite-xl/lib/font_renderer/agg_pixfmt_alpha8.h

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#pragma once
#include <string.h>
#include "agg_basics.h"
#include "agg_rendering_buffer.h"
namespace agg
{
// This is a special purpose color type that only has the alpha channel.
// It can be thought as a gray color but with the intensity always on.
// It is actually used to store coverage information.
struct alpha8
{
typedef int8u value_type;
typedef int32u calc_type;
typedef int32 long_type;
enum base_scale_e
{
base_shift = 8,
base_scale = 1 << base_shift,
base_mask = base_scale - 1
};
value_type a;
//--------------------------------------------------------------------
alpha8(unsigned a_=base_mask) :
a(int8u(a_)) {}
};
// Pixer format to store coverage information.
class pixfmt_alpha8
{
public:
typedef alpha8 color_type;
typedef int8u value_type;
typedef int32u calc_type;
typedef agg::rendering_buffer::row_data row_data;
//--------------------------------------------------------------------
pixfmt_alpha8(rendering_buffer& rb): m_rbuf(&rb)
{
}
//--------------------------------------------------------------------
unsigned width() const {
return m_rbuf->width();
}
unsigned height() const {
return m_rbuf->height();
}
// This method should never be called when using the scanline_u8.
// The use of scanline_p8 should be avoided because if does not works
// properly for rendering fonts because single hspan are split in many
// hline/hspan elements and pixel whitening happens.
void blend_hline(int x, int y, unsigned len,
const color_type& c, int8u cover)
{ }
void copy_hline(int x, int y, unsigned len, const color_type& c)
{
value_type* p = (value_type*) m_rbuf->row_ptr(y) + x;
do
{
*p = c.a;
p++;
}
while(--len);
}
//--------------------------------------------------------------------
void blend_solid_hspan(int x, int y,
unsigned len,
const color_type& c,
const int8u* covers)
{
value_type* p = (value_type*) m_rbuf->row_ptr(y) + x;
do
{
calc_type alpha = (calc_type(c.a) * (calc_type(*covers) + 1)) >> 8;
*p = alpha;
p++;
++covers;
}
while(--len);
}
private:
rendering_buffer* m_rbuf;
};
}