lite-xl/lib/font_renderer/font_renderer.cpp

310 lines
12 KiB
C++

#include "font_renderer.h"
#include "agg_lcd_distribution_lut.h"
#include "agg_pixfmt_rgb.h"
#include "agg_pixfmt_rgba.h"
#include "agg_gamma_lut.h"
#include "font_renderer_alpha.h"
typedef agg::blender_rgb_gamma<agg::rgba8, agg::order_bgra, agg::gamma_lut<> > blender_gamma_type;
class FontRendererImpl {
public:
// Conventional LUT values: (1./3., 2./9., 1./9.)
// The values below are fine tuned as in the Elementary Plot library.
FontRendererImpl(bool hinting, bool kerning, bool subpixel, float gamma_value) :
m_renderer(hinting, kerning, subpixel),
m_gamma_lut(double(gamma_value)),
m_blender(),
m_lcd_lut(0.448, 0.184, 0.092)
{
m_blender.gamma(m_gamma_lut);
}
font_renderer_alpha& renderer_alpha() { return m_renderer; }
blender_gamma_type& blender() { return m_blender; }
agg::gamma_lut<>& gamma() { return m_gamma_lut; }
agg::lcd_distribution_lut& lcd_distribution_lut() { return m_lcd_lut; }
private:
font_renderer_alpha m_renderer;
agg::gamma_lut<> m_gamma_lut;
blender_gamma_type m_blender;
agg::lcd_distribution_lut m_lcd_lut;
};
FontRenderer *FontRendererNew(unsigned int flags, float gamma) {
bool hinting = ((flags & FONT_RENDERER_HINTING) != 0);
bool kerning = ((flags & FONT_RENDERER_KERNING) != 0);
bool subpixel = ((flags & FONT_RENDERER_SUBPIXEL) != 0);
return new FontRendererImpl(hinting, kerning, subpixel, gamma);
}
void FontRendererFree(FontRenderer *font_renderer) {
delete font_renderer;
}
int FontRendererLoadFont(FontRenderer *font_renderer, const char *filename) {
bool success = font_renderer->renderer_alpha().load_font(filename);
return (success ? 0 : 1);
}
int FontRendererGetFontHeight(FontRenderer *font_renderer, float size) {
font_renderer_alpha& renderer_alpha = font_renderer->renderer_alpha();
double ascender, descender;
renderer_alpha.get_font_vmetrics(ascender, descender);
int face_height = renderer_alpha.get_face_height();
float scale = renderer_alpha.scale_for_em_to_pixels(size);
return int((ascender - descender) * face_height * scale + 0.5);
}
static void glyph_trim_rect(agg::rendering_buffer& ren_buf, GlyphBitmapInfo& gli, int subpixel_scale) {
const int height = ren_buf.height();
int x0 = gli.x0 * subpixel_scale, x1 = gli.x1 * subpixel_scale;
int y0 = gli.y0, y1 = gli.y1;
for (int y = gli.y0; y < gli.y1; y++) {
const uint8_t *row = ren_buf.row_ptr(height - 1 - y);
unsigned int row_bitsum = 0;
for (int x = x0; x < x1; x++) {
row_bitsum |= row[x];
}
if (row_bitsum == 0) {
y0++;
} else {
break;
}
}
for (int y = gli.y1 - 1; y >= y0; y--) {
const uint8_t *row = ren_buf.row_ptr(height - 1 - y);
unsigned int row_bitsum = 0;
for (int x = x0; x < x1; x++) {
row_bitsum |= row[x];
}
if (row_bitsum == 0) {
y1--;
} else {
break;
}
}
for (int x = gli.x0 * subpixel_scale; x < gli.x1 * subpixel_scale; x += subpixel_scale) {
unsigned int xaccu = 0;
for (int y = y0; y < y1; y++) {
const uint8_t *row = ren_buf.row_ptr(height - 1 - y);
for (int i = 0; i < subpixel_scale; i++) {
xaccu |= row[x + i];
}
}
if (xaccu == 0) {
x0 += subpixel_scale;
} else {
break;
}
}
for (int x = (gli.x1 - 1) * subpixel_scale; x >= x0; x -= subpixel_scale) {
unsigned int xaccu = 0;
for (int y = y0; y < y1; y++) {
const uint8_t *row = ren_buf.row_ptr(height - 1 - y);
for (int i = 0; i < subpixel_scale; i++) {
xaccu |= row[x + i];
}
}
if (xaccu == 0) {
x1 -= subpixel_scale;
} else {
break;
}
}
gli.xoff += (x0 / subpixel_scale) - gli.x0;
gli.yoff += (y0 - gli.y0);
gli.x0 = x0 / subpixel_scale;
gli.y0 = y0;
gli.x1 = x1 / subpixel_scale;
gli.y1 = y1;
}
static void glyph_lut_convolution(agg::rendering_buffer ren_buf, agg::lcd_distribution_lut& lcd_lut, agg::int8u *covers_buf, GlyphBitmapInfo& gli) {
const int subpixel = 3;
const int x0 = gli.x0, y0 = gli.y0, x1 = gli.x1, y1 = gli.y1;
const int len = (x1 - x0) * subpixel;
const int height = ren_buf.height();
for (int y = y0; y < y1; y++) {
agg::int8u *covers = ren_buf.row_ptr(height - 1 - y) + x0 * subpixel;
memcpy(covers_buf, covers, len);
for (int x = x0 - 1; x < x1 + 1; x++) {
for (int i = 0; i < subpixel; i++) {
const int cx = (x - x0) * subpixel + i;
covers[cx] = lcd_lut.convolution(covers_buf, cx, 0, len - 1);
}
}
}
gli.x0 -= 1;
gli.x1 += 1;
gli.xoff -= 1;
}
static int ceil_to_multiple(int n, int p) {
return p * ((n + p - 1) / p);
}
int FontRendererBakeFontBitmap(FontRenderer *font_renderer, int font_height,
void *pixels, int pixels_width, int pixels_height,
int first_char, int num_chars, GlyphBitmapInfo *glyphs, int subpixel_scale)
{
font_renderer_alpha& renderer_alpha = font_renderer->renderer_alpha();
const int pixel_size = 1;
memset(pixels, 0x00, pixels_width * pixels_height * subpixel_scale * pixel_size);
double ascender, descender;
renderer_alpha.get_font_vmetrics(ascender, descender);
const int ascender_px = int(ascender * font_height);
const int descender_px = ascender_px - font_height;
const int pad_y = font_height / 10;
const int y_step = font_height + 2 * pad_y;
agg::lcd_distribution_lut& lcd_lut = font_renderer->lcd_distribution_lut();
agg::rendering_buffer ren_buf((agg::int8u *) pixels, pixels_width * subpixel_scale, pixels_height, -pixels_width * subpixel_scale * pixel_size);
// When using subpixel font rendering it is needed to leave a padding pixel on the left and on the right.
// Since each pixel is composed by n subpixel we set below x_start to subpixel_scale instead than zero.
const int x_start = subpixel_scale;
int x = x_start, y = pixels_height - 1;
int res = 0;
const agg::alpha8 text_color(0xff);
#ifdef FONT_RENDERER_HEIGHT_HACK
const int font_height_reduced = (font_height * 86) / 100;
#else
const int font_height_reduced = font_height;
#endif
renderer_alpha.set_font_height(font_height_reduced);
agg::int8u *cover_swap_buffer = new agg::int8u[pixels_width * subpixel_scale];
for (int i = 0; i < num_chars; i++) {
int codepoint = first_char + i;
if (x + font_height * subpixel_scale > pixels_width * subpixel_scale) {
x = x_start;
y -= y_step;
}
if (y - y_step < 0) {
res = -1;
break;
}
const int y_baseline = y - pad_y - ascender_px;
double x_next = x, y_next = y_baseline;
renderer_alpha.render_codepoint(ren_buf, text_color, x_next, y_next, codepoint, subpixel_scale);
int x_next_i = (subpixel_scale == 1 ? int(x_next + 1.0) : ceil_to_multiple(x_next + 0.5, subpixel_scale));
// Below x and x_next_i will always be integer multiples of subpixel_scale.
GlyphBitmapInfo& glyph_info = glyphs[i];
glyph_info.x0 = x / subpixel_scale;
glyph_info.y0 = pixels_height - 1 - (y_baseline + ascender_px + pad_y); // FIXME: add -1 ?
glyph_info.x1 = x_next_i / subpixel_scale;
glyph_info.y1 = pixels_height - 1 - (y_baseline + descender_px - pad_y); // FIXME: add -1 ?
glyph_info.xoff = 0;
glyph_info.yoff = -pad_y;
glyph_info.xadvance = (x_next - x) / subpixel_scale;
#ifdef FONT_RENDERER_DEBUG
glyph_info.ybaseline = pixels_height - 1 - y_baseline;
#endif
if (glyph_info.x1 > glyph_info.x0) {
glyph_lut_convolution(ren_buf, lcd_lut, cover_swap_buffer, glyph_info);
}
glyph_trim_rect(ren_buf, glyph_info, subpixel_scale);
// When subpixel is activated we need one padding pixel on the left and on the right.
x = x_next_i + 2 * subpixel_scale;
}
delete [] cover_swap_buffer;
return res;
}
void blend_solid_hspan(agg::rendering_buffer& rbuf, blender_gamma_type& blender,
int x, int y, unsigned len,
const agg::rgba8& c, const agg::int8u* covers)
{
typedef typename blender_gamma_type::color_type color_type;
typedef typename blender_gamma_type::order_type order_type;
typedef typename color_type::value_type value_type;
typedef typename color_type::calc_type calc_type;
if (c.a)
{
value_type* p = (value_type*)rbuf.row_ptr(x, y, len) + (x << 2);
do
{
calc_type alpha = (calc_type(c.a) * (calc_type(*covers) + 1)) >> 8;
if(alpha == color_type::base_mask)
{
p[order_type::R] = c.r;
p[order_type::G] = c.g;
p[order_type::B] = c.b;
}
else
{
blender.blend_pix(p, c.r, c.g, c.b, alpha, *covers);
}
p += 4;
++covers;
}
while(--len);
}
}
void blend_solid_hspan_rgb_subpixel(agg::rendering_buffer& rbuf, agg::gamma_lut<>& gamma, agg::lcd_distribution_lut& lcd_lut,
int x, int y, unsigned len,
const agg::rgba8& c,
const agg::int8u* covers)
{
const int x_min = x;
const int x_max = x + len / 3;
const int pixel_size = 4;
const agg::int8u rgb[3] = { c.r, c.g, c.b };
agg::int8u* p = rbuf.row_ptr(y) + x_min * pixel_size;
// Indexes to adress RGB colors in a BGRA32 format.
const int pixel_index[3] = {2, 1, 0};
for (int xp = x_min; xp <= x_max; xp++)
{
for (int i = 0; i < 3; i++) {
int cx = xp * 3 - x + i;
unsigned cover_value = covers[cx];
unsigned alpha = (cover_value + 1) * (c.a + 1);
unsigned dst_col = gamma.dir(rgb[i]);
unsigned src_col = gamma.dir(*(p + pixel_index[i]));
*(p + pixel_index[i]) = gamma.inv((((dst_col - src_col) * alpha) + (src_col << 16)) >> 16);
}
// Leave p[3], the alpha channel value unmodified.
p += 4;
}
}
// destination implicitly BGRA32. Source implictly single-byte renderer_alpha coverage.
void FontRendererBlendGamma(FontRenderer *font_renderer, uint8_t *dst, int dst_stride, uint8_t *src, int src_stride, int region_width, int region_height, FontRendererColor color) {
blender_gamma_type& blender = font_renderer->blender();
agg::rendering_buffer dst_ren_buf(dst, region_width, region_height, dst_stride);
const agg::rgba8 color_a(color.r, color.g, color.b);
for (int x = 0, y = 0; y < region_height; y++) {
agg::int8u *covers = src + y * src_stride;
blend_solid_hspan(dst_ren_buf, blender, x, y, region_width, color_a, covers);
}
}
// destination implicitly BGRA32. Source implictly single-byte renderer_alpha coverage with subpixel scale = 3.
void FontRendererBlendGammaSubpixel(FontRenderer *font_renderer, uint8_t *dst, int dst_stride, uint8_t *src, int src_stride, int region_width, int region_height, FontRendererColor color) {
const int subpixel_scale = 3;
agg::gamma_lut<>& gamma = font_renderer->gamma();
agg::lcd_distribution_lut& lcd_lut = font_renderer->lcd_distribution_lut();
agg::rendering_buffer dst_ren_buf(dst, region_width, region_height, dst_stride);
const agg::rgba8 color_a(color.r, color.g, color.b);
for (int x = 0, y = 0; y < region_height; y++) {
agg::int8u *covers = src + y * src_stride;
blend_solid_hspan_rgb_subpixel(dst_ren_buf, gamma, lcd_lut, x, y, region_width * subpixel_scale, color_a, covers);
}
}