pimoroni-pico/libraries/pico_graphics/README.md

# Pico Graphics <!-- omit in toc -->

Pico Graphics is a tiny graphics library supporting a number of underlying buffer formats including 8-bit paletted (256 colour), 8-bit RGB332 (256 colour), 16-bit RGB565 (65K colour) and 4-bit packed (8 colour).

It supports drawing text, primitive and individual pixels and includes basic types such as `Rect` and `Point` brimming with methods to help you develop games and applications.

- [Overview](#overview)
  - [Pen Types](#pen-types)
  - [Creating A Pico Graphics Instance](#creating-a-pico-graphics-instance)
- [Function Reference](#function-reference)
  - [Types](#types)
    - [Rect](#rect)
      - [Rect.empty](#rectempty)
      - [Rect.contains](#rectcontains)
      - [Rect.intersects](#rectintersects)
      - [Rect.intersection](#rectintersection)
      - [Rect.inflate & Rect.deflate](#rectinflate--rectdeflate)
    - [Point](#point)
      - [Point.clamp](#pointclamp)
  - [Pens & Clipping](#pens--clipping)
    - [set_pen](#set_pen)
    - [create_pen](#create_pen)
    - [set_clip & remove_clip](#set_clip--remove_clip)
  - [Palette](#palette)
    - [update_pen](#update_pen)
    - [reset_pen](#reset_pen)
  - [Pixels](#pixels)
    - [pixel](#pixel)
    - [pixel_span](#pixel_span)
  - [Primitives](#primitives)
    - [rectangle](#rectangle)
    - [circle](#circle)
  - [Text](#text)
  - [Change Font](#change-font)


## Overview

Pico Graphics comes in multiple flavours depending on which underlying buffer type you wish to work with.

Your buffer doesn't have to be native to your display. For example a 16-bit ST7789 display can work with P4, P8, RGB332 and RGB565 buffers, with palette lookups handled for you on the fly.

A monochrome OLED display can currently only work with `1Bit` type buffers, and Inky Frame only with `3Bit`.

### Pen Types

* `1Bit` and `1BitY` - 1-bit packed, with automatic dithering from 16 shades of grey. 0 == Black, 15 == White. (For Inky Pack, or monochrome OLEDs)
* `3Bit` - 3-bit bitplaned, using three 1-bit buffers and supporting up to 8 colours. (For Inky Frame)
* `P4` - 4-bit packed, with an 8 colour palette. This is commonly used for 7/8-colour e-ink displays or driving large displays with few colours.
* `P8` - 8-bit, with a 256 colour palette. Great balance of memory usage versus available colours. You can replace palette entries on the fly.
* `RGB332` - 8-bit, with a fixed 256 colour RGB332 palette. Great for quickly porting an RGB565 app to use less RAM. Limits your colour choices, but is easier to grok.
* `RGB565` - 16-bit, 65K "True Colour." Great for rainbows, gradients and images but comes at the cost of RAM!

### Creating A Pico Graphics Instance

To create a Pico Graphics instance to draw into, you should construct an instance of the Pen type class you want to use:

```c++
PicoGraphics_Pen3Bit graphics(WIDTH, HEIGHT, nullptr);   // For Inky Frame
PicoGraphics_Pen1Bit graphics(WIDTH, HEIGHT, nullptr);   // For MonoChrome OLEDs
PicoGraphics_Pen1BitY graphics(WIDTH, HEIGHT, nullptr);  // For Inky Pack / Badger 2040
PicoGraphics_PenP4 graphics(WIDTH, HEIGHT, nullptr);     // For colour LCDs such as Pico Display
PicoGraphics_PenP8 graphics(WIDTH, HEIGHT, nullptr);     // ditto- uses 2x the RAM of P4
PicoGraphics_PenRGB332 graphics(WIDTH, HEIGHT, nullptr); // ditto
PicoGraphics_PenRGB565 graphics(WIDTH, HEIGHT, nullptr); // For 16-bit colour LCDs. Uses 2x the RAM of P8 or RGB332 but permits 65K colour.
```

To draw something to a display you should create a display driver instance, eg:

```c++
ST7789 st7789(PicoExplorer::WIDTH, PicoExplorer::HEIGHT, ROTATE_0, false, get_spi_pins(BG_SPI_FRONT));
```

And then send it the Pico Graphics instance to draw:

```c++
st7789.update(&graphics);
```

The driver will check your graphics type and act accordingly.

## Function Reference

### Types

#### Rect

The `Rect` type describes a rectangle in terms of its x, y position, width and height.

##### Rect.empty

```c++
bool Rect::empty();
```

##### Rect.contains

```c++
bool Rect::contains(const Rect &p);
```

`contains` allows you to check if a `Rect` contains a specific `Point`. This can be useful for checking collissions (have I clicked on something?):

```c++
Point cursor(50, 50);
Rect widget(0, 0, 100, 100);
bool hover = widet.contains(cursor);
```

##### Rect.intersects

```c++
bool Rect::intersects(const Rect &r);
```

`intersects` allows you to check if a `Rect` intersects or overlaps another `Rect`, for example these rectangles do not intersect:

```c++
Rect a(10, 10, 10, 10);
Rect b(30, 10, 10, 10);
a.intersects(b) == false
```

And these do:

```c++
Rect a(10, 10, 10, 10);
Rect b(15, 10, 10, 10);
a.intersects(b) == true
```

##### Rect.intersection

```c++
Rect Rect::intersection(const Rect &r);
```

`intersection` takes an input `Rect` and returns a new `Rect` that describes the region in which the two `Rect`s overlap. For example:

```c++
Rect a(0, 0, 10, 20);
Rect b(0, 0, 20, 10);
Rect c = a.intersection(b);
```

In this case `c` would equal `Rect c(0, 0, 10, 10);` since this is the region that `a` and `b` overlap.


##### Rect.inflate & Rect.deflate

```c++
void Rect::inflate(int32_t v);
void Rect::declate(int32_t v);
```

`inflate` will inflate a `Rect`, like a balooon, by adding the number of pixels you specify to all sides. For example:

```c++
Rect box(10, 10, 10, 10);
box.inflate(10);
```

Would inflate our `box` to start at 0,0 and be 30x30 pixels in size.

`deflate` does the opposite:

```c++
Rect box(10, 10, 10, 10);
box.deflate(1);
```

Would deflate our `box` to start at `11,11` and be 8x8 pixels in size.

Since `rectangle` *always* draws a filled rectangle, this can be useful to add an outline of your desired thickness:

```c++
WHITE = graphics.create_pen(255, 255, 255);
Rect box(10, 10, 100, 100);
box.inflate(1); // Inflate our box by 1px on all sides
graphics.set_pen(WHITE); // White outline
graphics.rectangle(box);
box.deflate(1); // Return to our original box size
graphics.set_pen(0, 0, 0); /// Black fill
graphics.rectangle(box);
```

#### Point

The `Point` type describes a single point - synonymous with a pixel - in terms of its x and y position.

##### Point.clamp

```c++
Point Point::clamp(const Rect &r);
```

A point can be clamped within the confines of a `Rect`. This is useful for keeping - for example - a cursor within the bounds of the screen:

```c++
Point cursor(10, 1000);       // A point, far outside the bounds of our screen
cursor.clamp(graphics.bounds);  // Clamp to the screen
```

### Pens & Clipping

#### set_pen

In order to draw anything with Pico Graphics you must first set the pen to your desired palette colour:

```c++
void PicoGraphics::set_pen(uint8_t p);
```

This value represents an index into the internal colour palette, which has 256 entries and defaults to RGB332 giving an approximation of all RGB888 colours.


#### create_pen

```c++
int PicoGraphics::create_pen(uint8_t r, uint8_t g, uint8_t b);
```

By default create pen takes R, G and B values, clamps them to 3, 3 and 2 bits respectively and returns an index in the RGB332 palette.

You must create pens before using them with `set_pen()` which accepts only a palette index.

#### set_clip & remove_clip

```c++
void PicoGraphics::set_clip(const Rect &r);
void PicoGraphics::remove_clip();
```

`set_clip` applies a clipping rectangle to the drawing surface. Any pixels outside of this rectangle will not be drawn. By default drawing operations are clipped to `bounds` since it's impossible to draw outside of the buffer.

`remove_clip` sets the surface clipping rectangle back to the surface `bounds`.

### Palette

If you construct an instance of PicoGraphics with `PicoGraphics_PenRGB332` all colour values (created pens) will be clamped to their `RGB332` equivalent values.

This will give you an approximate colour for every RGB888 value you request, but only a fixed palette of 256 total colours is actually supported and displayed on screen.

If you don't want to think about or manage a palette of custom colours, `RGB332` is the way to go.

If you wish to choose your own custom palette you should use either `PicoGraphics_PenP8` or `PicoGraphics_PenP4` which support up to 256 and 16 colours respectively.

Internally all colours are stored as RGB888 and converted when they are displayed on your screen.

#### update_pen

```c++
int PicoGraphics::update_pen(uint8_t index, uint8_t r, uint8_t g, uint8_t b);
```

Modify a palette entry to the given RGB colour (or nearest supported equivilent.)

#### reset_pen

```c++
void PicoGraphics::reset_pen(uint8_t index);
```

Return a palette entry to its default value. Usually black and marked unused.

### Pixels

#### pixel

```c++
void PicoGraphics::pixel(const Point &p);
```

`pixel` sets the pixel at `Point p` to the current `pen`.

#### pixel_span

```c++
void PicoGraphics::pixel_span(const Point &p, int32_t l)
```

`pixel_span` draws a horizontal line of pixels of length `int32_t l` starting at `Point p`.

### Primitives

#### rectangle

```c++
void PicoGraphics::rectangle(const Rect &r) ;
```

`rectangle` draws a filled rectangle described by `Rect`.

#### circle

```c++
PicoGraphics::circle(const Point &p, int32_t radius) 
```

`circle` draws a filled circle centered on `Point p` with radius `int32_t radius`.

### Text

```c++
void PicoGraphics::text(const std::string &t, const Point &p, int32_t wrap, uint8_t scale);
```

`text` allows you to draw a string at `Point p`, with a maximum line-width of `int32_t wrap`.

The 6x6 and 6x8 pixel font characters are encoded in `font6_data.hpp` and `font8_data.hpp` along with their character widths so that text can be drawn variable-width.

You can scale text with `uint8_t scale` for 12x12, 18x18, etc character sizes.

### Change Font

```c++
void PicoGraphics::set_font(const Font *font);
```


`set_font` allows you to change the font that PicoGraphics uses to draw text.

If you:

```c++
#include "font8_data.hpp"
```

Then you can: `set_font(&font8);` to use a font with upper/lowercase characters.