Draw text

bricks/_common/sources.mk

@@ -207,6 +207,8 @@ PBIO_SRC_C = $(addprefix lib/pbio/,\
 	src/drivebase.c \
 	src/error.c \
 	src/geometry.c \
+	src/image/font_liberationsans_regular_14.c \
+	src/image/font_terminus_normal_16.c \
 	src/image/image.c \
 	src/imu.c \
 	src/int_math.c \

lib/pbio/include/pbio/font.h

@@ -0,0 +1,116 @@
+// SPDX-License-Identifier: MIT
+// Copyright (c) 2025 Nicolas Schodet
+
+/**
+ * @addtogroup Font Text font.
+ * @{
+ */
+
+#ifndef _PBIO_FONT_H_
+#define _PBIO_FONT_H_
+
+#include <pbio/config.h>
+
+#include <stdint.h>
+
+/**
+ * Single glyph.
+ */
+typedef struct _pbio_font_glyph_t {
+    /**
+     * Width of glyph bitmap.
+     */
+    uint8_t width;
+    /**
+     * Height of glyph bitmap.
+     */
+    uint8_t height;
+    /**
+     * Advance to next character in horizontal direction.
+     */
+    uint8_t advance;
+    /**
+     * Horizontal distance between pen position and leftmost bitmap column.
+     * Positive values goes left.
+     */
+    int8_t left;
+    /**
+     * Vertical distance between baseline and topmost bitmap row. Positive
+     * values goes up.
+     */
+    int8_t top;
+    /**
+     * Index of bitmap start in data table.
+     */
+    uint16_t data_index;
+    /**
+     * Start index of kerning values in kerning table. The Stop index is the
+     * start index of the next glyph.
+     */
+    uint16_t kerning_index;
+} pbio_font_glyph_t;
+
+/**
+ * Kerning information for a glyph.
+ */
+typedef struct _pbio_font_kerning_t {
+    /**
+     * Previous glyph.
+     */
+    uint8_t previous;
+    /**
+     * Kerning from previous glyph to current one.
+     */
+    int8_t kerning;
+} pbio_font_kerning_t;
+
+/**
+ * Font.
+ *
+ * Every bitmap data is composed of one or several rows as indicated in the
+ * glyph structure, with the top row first. Eight pixels are packed into
+ * a bytes, with the first leftmost pixel in the most significant bit. The
+ * bitmap width is padded to the next multiple of eight.
+ */
+typedef struct _pbio_font_t {
+    /**
+     * First glyph.
+     */
+    uint8_t first;
+    /**
+     * Last glyph.
+     */
+    uint8_t last;
+    /**
+     * Line height, number of pixels between consecutive baselines.
+     */
+    uint8_t line_height;
+    /**
+     * Maximum value of glyph top.
+     */
+    int8_t top_max;
+    /**
+     * Glyph table. Must contain a dummy last glyph for the last kerning stop
+     * index.
+     */
+    const pbio_font_glyph_t *glyphs;
+    /**
+     * Data table with bitmaps.
+     */
+    const uint8_t *data;
+    /**
+     * Kerning table, may be NULL if no kerning.
+     */
+    const pbio_font_kerning_t *kernings;
+} pbio_font_t;
+
+#if PBIO_CONFIG_IMAGE
+
+extern const pbio_font_t pbio_font_liberationsans_regular_14;
+extern const pbio_font_t pbio_font_terminus_normal_16;
+
+#endif // PBIO_CONFIG_IMAGE
+
+#endif // _PBIO_FONT_H_
+
+/** @} */

lib/pbio/include/pbio/image.h

@@ -10,8 +10,10 @@
 #define _PBIO_IMAGE_H_
 
 #include <pbio/config.h>
+#include <pbio/font.h>
 
 #include <stdint.h>
+#include <stddef.h>
 
 /**
  * Image container.
@@ -51,6 +53,28 @@ typedef struct _pbio_image_t {
     int stride;
 } pbio_image_t;
 
+/**
+ * Coordinates of a rectangle.
+ */
+typedef struct _pbio_image_rect_t {
+    /**
+     * X coordinate.
+     */
+    int x;
+    /**
+     * Y coordinate.
+     */
+    int y;
+    /**
+     * Number of columns.
+     */
+    int width;
+    /**
+     * Number of rows.
+     */
+    int height;
+} pbio_image_rect_t;
+
 #if PBIO_CONFIG_IMAGE
 
 void pbio_image_init(pbio_image_t *image, uint8_t *pixels, int width,
@@ -99,6 +123,12 @@ void pbio_image_draw_circle(pbio_image_t *image, int x, int y, int r,
 void pbio_image_fill_circle(pbio_image_t *image, int x, int y, int r,
     uint8_t value);
 
+void pbio_image_draw_text(pbio_image_t *image, const pbio_font_t *font, int x,
+    int y, const char *text, size_t text_len, uint8_t value);
+
+void pbio_image_bbox_text(const pbio_font_t *font, const char *text,
+    size_t text_len, pbio_image_rect_t *rect);
+
 #endif // PBIO_CONFIG_IMAGE
 
 #endif // _PBIO_IMAGE_H_

lib/pbio/src/image/Makefile

@@ -0,0 +1,25 @@
+# Use this Makefile to generate font files.
+
+FONTCONVERT = ../../tools/fontconvert.py
+
+LIBERATION_LICENSE = "OFL-1.1-RFN"
+LIBERATION_COPYRIGHT = \
+	--copyright "Digitized data copyright (c) 2010 Google Corporation" \
+	--copyright "  with Reserved Font Arimo, Tinos and Cousine." \
+	--copyright "Copyright (c) 2012 Red Hat, Inc." \
+	--copyright "  with Reserved Font Name Liberation."
+LIBERATION_SANS_REGULAR = /usr/share/fonts/truetype/liberation/LiberationSans-Regular.ttf
+
+TERMINUS_LICENSE = "OFL-1.1-RFN"
+TERMINUS_COPYRIGHT = \
+	--copyright "Copyright (c) 2010-2014 Dimitar Toshkov Zhekov," \
+	--copyright '  with Reserved Font Name "Terminus Font".'
+TERMINUS_NORMAL = /usr/share/fonts/opentype/terminus/terminus-normal.otb
+
+all: font_liberationsans_regular_14.c font_terminus_normal_16.c
+
+font_liberationsans_regular_14.c: $(LIBERATION_SANS_REGULAR) $(FONTCONVERT)
+	python3 $(FONTCONVERT) $< 14 --license $(LIBERATION_LICENSE) $(LIBERATION_COPYRIGHT) > $@
+
+font_terminus_normal_16.c: $(TERMINUS_NORMAL) $(FONTCONVERT)
+	python3 $(FONTCONVERT) $< 16 --license $(TERMINUS_LICENSE) $(TERMINUS_COPYRIGHT) > $@