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add func blend_pixel to fix font rendering issues on transparent backgrounds(SUBPIXEL)

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xueshuming
2025-05-28 20:55:38 +08:00
parent 6aa294e75b
commit 4cf4d204e7
1 changed files with 81 additions and 9 deletions
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90
src/newgdi/glyph.c
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@@ -1092,6 +1092,67 @@ nodraw_ret:
}
#ifdef _MGFONT_FT2
static RGB blend_pixel(RGB font_pixel, RGB fg_color, RGB bg_color)
{
RGB result;
Uint8 src_pre_r, src_pre_g, src_pre_b;
Uint8 bg_pre_r, bg_pre_g, bg_pre_b, alpha_bg;
Uint8 out_r, out_g, out_b, alpha_out;
uint8_t alpha_font = 0.299 * font_pixel.r + 0.587 * font_pixel.g +
0.114 * font_pixel.b;
uint16_t alpha_src = (fg_color.a * alpha_font + 127) / 255;
if (alpha_src == 0) {
result = bg_color;
goto out;
}
src_pre_r = (fg_color.r * alpha_src + 127) / 255;
src_pre_g = (fg_color.g * alpha_src + 127) / 255;
src_pre_b = (fg_color.b * alpha_src + 127) / 255;
bg_pre_r = (bg_color.r * bg_color.a + 127) / 255;
bg_pre_g = (bg_color.g * bg_color.a + 127) / 255;
bg_pre_b = (bg_color.b * bg_color.a + 127) / 255;
alpha_bg = bg_color.a;
out_r = src_pre_r + (bg_pre_r * (255 - alpha_src)) / 255;
out_g = src_pre_g + (bg_pre_g * (255 - alpha_src)) / 255;
out_b = src_pre_b + (bg_pre_b * (255 - alpha_src)) / 255;
alpha_out = alpha_src + (alpha_bg * (255 - alpha_src)) / 255;
if (out_r > 255) {
out_r = 255;
}
if (out_g > 255) {
out_g = 255;
}
if (out_b > 255) {
out_b = 255;
}
if (alpha_out > 0) {
result.r = (out_r * 255 + alpha_out / 2) / alpha_out;
result.g = (out_g * 255 + alpha_out / 2) / alpha_out;
result.b = (out_b * 255 + alpha_out / 2) / alpha_out;
result.a = (uint8_t) alpha_out;
} else {
result.r = 0;
result.g = 0;
result.b = 0;
result.a = 0;
}
out:
return result;
}
static void _dc_ft2subpixel_scan_line(PDC pdc, int xpos, int ypos,
SCANLINE_CTXT* ctxt)
{
@@ -1112,8 +1173,8 @@ static void _dc_ft2subpixel_scan_line(PDC pdc, int xpos, int ypos,
ctxt->glyph_ascent, ctxt->glyph_line,
ctxt->glyph_advance);
GAL_GetRGB (pdc->textcolor, pdc->surface->format, &rgba_fg.r,
&rgba_fg.g, &rgba_fg.b);
GAL_GetRGBA (pdc->textcolor, pdc->surface->format, &rgba_fg.r,
&rgba_fg.g, &rgba_fg.b, &rgba_fg.a);
for (x = 0; x < ctxt->bmp_w; x++) {
if (!PtInRect (&pdc->rc_output, x+xpos, ypos)) {
@@ -1130,8 +1191,8 @@ static void _dc_ft2subpixel_scan_line(PDC pdc, int xpos, int ypos,
_glyph_move_to_pixel (pdc, x+xpos, ypos);
pixel = _mem_get_pixel(pdc->cur_dst, GAL_BytesPerPixel (pdc->surface));
GAL_GetRGB (pixel, pdc->surface->format, &rgba_cur.r,
&rgba_cur.g, &rgba_cur.b);
GAL_GetRGBA (pixel, pdc->surface->format, &rgba_cur.r,
&rgba_cur.g, &rgba_cur.b, &rgba_cur.a);
#define C_ALPHA(p, Cs, Cd) \
if (*p++) { \
@@ -1140,14 +1201,25 @@ static void _dc_ft2subpixel_scan_line(PDC pdc, int xpos, int ypos,
Cd = sub_val >> 8; \
}
C_ALPHA(bits, rgba_fg.r, rgba_cur.r);
C_ALPHA(bits, rgba_fg.g, rgba_cur.g);
C_ALPHA(bits, rgba_fg.b, rgba_cur.b);
if (rgba_cur.r == 0 && rgba_cur.g == 0 && rgba_cur.b == 0 &&
rgba_cur.a == 0) {
RGB font_pixel = {bits[0], bits[1], bits[2], 255};
RGB ret = blend_pixel(font_pixel, rgba_fg, rgba_cur);
rgba_cur = ret;
bits += 3;
}
else {
C_ALPHA(bits, rgba_fg.r, rgba_cur.r);
C_ALPHA(bits, rgba_fg.g, rgba_cur.g);
C_ALPHA(bits, rgba_fg.b, rgba_cur.b);
rgba_cur.a = 255.0;
}
#undef C_ALPHA
pdc->cur_pixel = GAL_MapRGB (pdc->surface->format, rgba_cur.r,
rgba_cur.g, rgba_cur.b);
pdc->cur_pixel = GAL_MapRGBA (pdc->surface->format, rgba_cur.r,
rgba_cur.g, rgba_cur.b, rgba_cur.a);
if (pdc->cur_pixel != pixel) {
_glyph_draw_pixel (pdc, x+xpos, ypos, pdc->cur_pixel);