Francesco Abbate
f5ede27e91
Text looks more correct without the gamma correction. With gamma correction text looks too bold in dark mode and too light in light mode. This behavior is a sign that gamma correction is not the right thing to do. The problem is seen with gamma at 1.5 used previously but is even worst if a gamma value of 2.2, the theoretical value, is used.
328 lines
12 KiB
C++
328 lines
12 KiB
C++
#include "font_renderer.h"
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#include "agg_lcd_distribution_lut.h"
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#include "agg_pixfmt_rgb.h"
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#include "agg_pixfmt_rgba.h"
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#include "font_renderer_alpha.h"
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// Important: when a subpixel scale is used the width below will be the width in logical pixel.
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// As each logical pixel contains 3 subpixels it means that the 'pixels' pointer
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// will hold enough space for '3 * width' uint8_t values.
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struct FR_Bitmap {
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agg::int8u *pixels;
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int width, height;
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};
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class FR_Impl {
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public:
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// Conventional LUT values: (1./3., 2./9., 1./9.)
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// The values below are fine tuned as in the Elementary Plot library.
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FR_Impl(bool hinting, bool kerning, bool subpixel, bool prescale_x) :
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m_renderer(hinting, kerning, subpixel, prescale_x),
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m_lcd_lut(0.448, 0.184, 0.092),
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m_subpixel(subpixel)
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{ }
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font_renderer_alpha& renderer_alpha() { return m_renderer; }
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agg::lcd_distribution_lut& lcd_distribution_lut() { return m_lcd_lut; }
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int subpixel_scale() const { return (m_subpixel ? 3 : 1); }
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private:
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font_renderer_alpha m_renderer;
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agg::lcd_distribution_lut m_lcd_lut;
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int m_subpixel;
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};
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FR_Renderer *FR_Renderer_New(unsigned int flags) {
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bool hinting = ((flags & FR_HINTING) != 0);
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bool kerning = ((flags & FR_KERNING) != 0);
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bool subpixel = ((flags & FR_SUBPIXEL) != 0);
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bool prescale_x = ((flags & FR_PRESCALE_X) != 0);
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return new FR_Impl(hinting, kerning, subpixel, prescale_x);
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}
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FR_Bitmap* FR_Bitmap_New(FR_Renderer *font_renderer, int width, int height) {
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const int subpixel_scale = font_renderer->subpixel_scale();
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FR_Bitmap *image = (FR_Bitmap *) malloc(sizeof(FR_Bitmap) + width * height * subpixel_scale);
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if (!image) { return NULL; }
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image->pixels = (agg::int8u *) (image + 1);
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image->width = width;
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image->height = height;
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return image;
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}
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void FR_Bitmap_Free(FR_Bitmap *image) {
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free(image);
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}
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void FR_Renderer_Free(FR_Renderer *font_renderer) {
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delete font_renderer;
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}
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int FR_Load_Font(FR_Renderer *font_renderer, const char *filename) {
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bool success = font_renderer->renderer_alpha().load_font(filename);
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return (success ? 0 : 1);
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}
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int FR_Get_Font_Height(FR_Renderer *font_renderer, float size) {
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font_renderer_alpha& renderer_alpha = font_renderer->renderer_alpha();
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double ascender, descender;
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renderer_alpha.get_font_vmetrics(ascender, descender);
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int face_height = renderer_alpha.get_face_height();
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float scale = renderer_alpha.scale_for_em_to_pixels(size);
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return int((ascender - descender) * face_height * scale + 0.5);
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}
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static void glyph_trim_rect(agg::rendering_buffer& ren_buf, FR_Bitmap_Glyph_Metrics& gli, int subpixel_scale) {
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const int height = ren_buf.height();
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int x0 = gli.x0 * subpixel_scale, x1 = gli.x1 * subpixel_scale;
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int y0 = gli.y0, y1 = gli.y1;
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for (int y = gli.y0; y < gli.y1; y++) {
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const uint8_t *row = ren_buf.row_ptr(height - 1 - y);
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unsigned int row_bitsum = 0;
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for (int x = x0; x < x1; x++) {
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row_bitsum |= row[x];
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}
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if (row_bitsum == 0) {
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y0++;
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} else {
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break;
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}
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}
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for (int y = gli.y1 - 1; y >= y0; y--) {
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const uint8_t *row = ren_buf.row_ptr(height - 1 - y);
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unsigned int row_bitsum = 0;
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for (int x = x0; x < x1; x++) {
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row_bitsum |= row[x];
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}
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if (row_bitsum == 0) {
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y1--;
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} else {
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break;
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}
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}
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for (int x = gli.x0 * subpixel_scale; x < gli.x1 * subpixel_scale; x += subpixel_scale) {
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unsigned int xaccu = 0;
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for (int y = y0; y < y1; y++) {
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const uint8_t *row = ren_buf.row_ptr(height - 1 - y);
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for (int i = 0; i < subpixel_scale; i++) {
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xaccu |= row[x + i];
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}
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}
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if (xaccu == 0) {
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x0 += subpixel_scale;
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} else {
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break;
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}
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}
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for (int x = (gli.x1 - 1) * subpixel_scale; x >= x0; x -= subpixel_scale) {
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unsigned int xaccu = 0;
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for (int y = y0; y < y1; y++) {
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const uint8_t *row = ren_buf.row_ptr(height - 1 - y);
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for (int i = 0; i < subpixel_scale; i++) {
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xaccu |= row[x + i];
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}
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}
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if (xaccu == 0) {
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x1 -= subpixel_scale;
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} else {
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break;
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}
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}
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gli.xoff += (x0 / subpixel_scale) - gli.x0;
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gli.yoff += (y0 - gli.y0);
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gli.x0 = x0 / subpixel_scale;
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gli.y0 = y0;
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gli.x1 = x1 / subpixel_scale;
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gli.y1 = y1;
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}
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static void glyph_lut_convolution(agg::rendering_buffer ren_buf, agg::lcd_distribution_lut& lcd_lut, agg::int8u *covers_buf, FR_Bitmap_Glyph_Metrics& gli) {
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const int subpixel = 3;
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const int x0 = gli.x0, y0 = gli.y0, x1 = gli.x1, y1 = gli.y1;
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const int len = (x1 - x0) * subpixel;
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const int height = ren_buf.height();
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for (int y = y0; y < y1; y++) {
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agg::int8u *covers = ren_buf.row_ptr(height - 1 - y) + x0 * subpixel;
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memcpy(covers_buf, covers, len);
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for (int x = x0 - 1; x < x1 + 1; x++) {
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for (int i = 0; i < subpixel; i++) {
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const int cx = (x - x0) * subpixel + i;
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covers[cx] = lcd_lut.convolution(covers_buf, cx, 0, len - 1);
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}
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}
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}
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gli.x0 -= 1;
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gli.x1 += 1;
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gli.xoff -= 1;
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}
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static int ceil_to_multiple(int n, int p) {
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return p * ((n + p - 1) / p);
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}
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int FR_Bake_Font_Bitmap(FR_Renderer *font_renderer, int font_height,
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FR_Bitmap *image,
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int first_char, int num_chars, FR_Bitmap_Glyph_Metrics *glyphs)
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{
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font_renderer_alpha& renderer_alpha = font_renderer->renderer_alpha();
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agg::lcd_distribution_lut& lcd_lut = font_renderer->lcd_distribution_lut();
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const int subpixel_scale = font_renderer->subpixel_scale();
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agg::int8u *pixels = image->pixels;
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const int pixels_width = image->width, pixels_height = image->height;
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const int pixel_size = 1;
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memset(pixels, 0x00, pixels_width * pixels_height * subpixel_scale * pixel_size);
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double ascender, descender;
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renderer_alpha.get_font_vmetrics(ascender, descender);
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const int ascender_px = int(ascender * font_height);
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const int descender_px = ascender_px - font_height;
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const int pad_y = font_height / 10;
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const int y_step = font_height + 2 * pad_y;
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agg::rendering_buffer ren_buf(pixels, pixels_width * subpixel_scale, pixels_height, -pixels_width * subpixel_scale * pixel_size);
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// When using subpixel font rendering it is needed to leave a padding pixel on the left and on the right.
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// Since each pixel is composed by n subpixel we set below x_start to subpixel_scale instead than zero.
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const int x_start = subpixel_scale;
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int x = x_start, y = pixels_height - 1;
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int res = 0;
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const agg::alpha8 text_color(0xff);
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#ifdef FONT_RENDERER_HEIGHT_HACK
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const int font_height_reduced = (font_height * 86) / 100;
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#else
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const int font_height_reduced = font_height;
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#endif
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renderer_alpha.set_font_height(font_height_reduced);
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agg::int8u *cover_swap_buffer = new agg::int8u[pixels_width * subpixel_scale];
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for (int i = 0; i < num_chars; i++) {
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int codepoint = first_char + i;
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if (x + font_height * subpixel_scale > pixels_width * subpixel_scale) {
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x = x_start;
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y -= y_step;
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}
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if (y - y_step < 0) {
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res = -1;
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break;
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}
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const int y_baseline = y - pad_y - ascender_px;
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double x_next = x, y_next = y_baseline;
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renderer_alpha.render_codepoint(ren_buf, text_color, x_next, y_next, codepoint, subpixel_scale);
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int x_next_i = (subpixel_scale == 1 ? int(x_next + 1.0) : ceil_to_multiple(x_next + 0.5, subpixel_scale));
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// Below x and x_next_i will always be integer multiples of subpixel_scale.
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FR_Bitmap_Glyph_Metrics& glyph_info = glyphs[i];
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glyph_info.x0 = x / subpixel_scale;
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glyph_info.y0 = pixels_height - 1 - (y_baseline + ascender_px + pad_y); // FIXME: add -1 ?
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glyph_info.x1 = x_next_i / subpixel_scale;
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glyph_info.y1 = pixels_height - 1 - (y_baseline + descender_px - pad_y); // FIXME: add -1 ?
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glyph_info.xoff = 0;
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glyph_info.yoff = -pad_y;
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glyph_info.xadvance = (x_next - x) / subpixel_scale;
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if (subpixel_scale != 1 && glyph_info.x1 > glyph_info.x0) {
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glyph_lut_convolution(ren_buf, lcd_lut, cover_swap_buffer, glyph_info);
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}
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glyph_trim_rect(ren_buf, glyph_info, subpixel_scale);
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// When subpixel is activated we need one padding pixel on the left and on the right.
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x = x_next_i + 2 * subpixel_scale;
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}
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delete [] cover_swap_buffer;
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return res;
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}
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template <typename Order>
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void blend_solid_hspan(agg::rendering_buffer& rbuf, int x, int y, unsigned len,
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const agg::rgba8& c, const agg::int8u* covers)
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{
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const int pixel_size = 4;
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agg::int8u* p = rbuf.row_ptr(y) + x * pixel_size;
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do
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{
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const unsigned alpha = *covers;
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const unsigned r = p[Order::R], g = p[Order::G], b = p[Order::B];
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p[Order::R] = (((unsigned(c.r) - r) * alpha) >> 8) + r;
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p[Order::G] = (((unsigned(c.g) - g) * alpha) >> 8) + g;
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p[Order::B] = (((unsigned(c.b) - b) * alpha) >> 8) + b;
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// Leave p[3], the alpha channel value unmodified.
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p += 4;
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++covers;
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}
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while(--len);
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}
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template <typename Order>
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void blend_solid_hspan_subpixel(agg::rendering_buffer& rbuf, agg::lcd_distribution_lut& lcd_lut,
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const int x, const int y, unsigned len,
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const agg::rgba8& c,
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const agg::int8u* covers)
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{
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const int pixel_size = 4;
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const unsigned rgb[3] = { c.r, c.g, c.b };
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agg::int8u* p = rbuf.row_ptr(y) + x * pixel_size;
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// Indexes to adress RGB colors in a BGRA32 format.
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const int pixel_index[3] = {Order::R, Order::G, Order::B};
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for (unsigned cx = 0; cx < len; cx += 3)
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{
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for (int i = 0; i < 3; i++) {
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const unsigned cover_value = covers[cx + i];
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const unsigned alpha = (cover_value + 1) * (c.a + 1);
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const unsigned src_col = *(p + pixel_index[i]);
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*(p + pixel_index[i]) = (((rgb[i] - src_col) * alpha) + (src_col << 16)) >> 16;
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}
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// Leave p[3], the alpha channel value unmodified.
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p += 4;
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}
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}
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// destination implicitly BGRA32. Source implictly single-byte renderer_alpha coverage with subpixel scale = 3.
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// FIXME: consider using something like RenColor* instead of uint8_t * for dst.
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void FR_Blend_Glyph(FR_Renderer *font_renderer, FR_Clip_Area *clip, int x, int y, uint8_t *dst, int dst_width, const FR_Bitmap *glyphs_bitmap, const FR_Bitmap_Glyph_Metrics *glyph, FR_Color color) {
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agg::lcd_distribution_lut& lcd_lut = font_renderer->lcd_distribution_lut();
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const int subpixel_scale = font_renderer->subpixel_scale();
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const int pixel_size = 4; // Pixel size for BGRA32 format.
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x += glyph->xoff;
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y += glyph->yoff;
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int glyph_x = glyph->x0, glyph_y = glyph->y0;
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int glyph_width = glyph->x1 - glyph->x0;
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int glyph_height = glyph->y1 - glyph->y0;
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int n;
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if ((n = clip->left - x) > 0) { glyph_width -= n; glyph_x += n; x += n; }
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if ((n = clip->top - y) > 0) { glyph_height -= n; glyph_y += n; y += n; }
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if ((n = x + glyph_width - clip->right ) > 0) { glyph_width -= n; }
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if ((n = y + glyph_height - clip->bottom) > 0) { glyph_height -= n; }
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if (glyph_width <= 0 || glyph_height <= 0) {
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return;
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}
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dst += (x + y * dst_width) * pixel_size;
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agg::rendering_buffer dst_ren_buf(dst, glyph_width, glyph_height, dst_width * pixel_size);
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uint8_t *src = glyphs_bitmap->pixels + (glyph_x + glyph_y * glyphs_bitmap->width) * subpixel_scale;
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int src_stride = glyphs_bitmap->width * subpixel_scale;
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const agg::rgba8 color_a(color.r, color.g, color.b);
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for (int x = 0, y = 0; y < glyph_height; y++) {
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agg::int8u *covers = src + y * src_stride;
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if (subpixel_scale == 1) {
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blend_solid_hspan<agg::order_bgra>(dst_ren_buf, x, y, glyph_width, color_a, covers);
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} else {
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blend_solid_hspan_subpixel<agg::order_bgra>(dst_ren_buf, lcd_lut, x, y, glyph_width * subpixel_scale, color_a, covers);
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}
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}
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}
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