Picture management

libcasio manages picture formats.

The pixel

casio_pixel_t

A pixel represented as a 32-bit integer, encoded as 0x00RRGGBB using native endianness, which is used as the canonical form of representing a picture in libcasio.

casio_pixel_t casio_pixel(int r, int g, int b)

Function-like macro to create a pixel.

casio_pixel_t casio_pixel_with_r(casio_pixel_t pix, int r)

Replace the red component of a pixel with the given value.

casio_pixel_t casio_pixel_with_g(casio_pixel_t pix, int g)

Replace the green component of a pixel with the given value.

casio_pixel_t casio_pixel_with_b(casio_pixel_t pix, int b)

Replace the blue component of a pixel with the given value.

int casio_pixel_r(casio_pixel_t pix)

Get the red component of a pixel.

int casio_pixel_g(casio_pixel_t pix)

Get the green component of a pixel.

int casio_pixel_b(casio_pixel_t pix)

Get the blue component of a pixel.

Picture encodings

casio_colorcode_t

Color codes for the casio_pictureformat_4bit_code picture encoding.

casio_colorcode_black

Black: 0x000000.

casio_colorcode_blue

Blue: 0x0000FF.

casio_colorcode_green

Green: 0x00FF00.

casio_colorcode_cyan

Cyan: 0x00FFFF.

casio_colorcode_red

Red: 0xFF0000.

casio_colorcode_magenta

Magenta: 0xFF00FF.

casio_colorcode_yellow

Yellow: 0xFFFF00.

casio_colorcode_white

White: 0xFFFFFF.

casio_pictureformat_t

The picture format type.

By default, the pixels of a picture are defined top to bottom, left to right.

casio_pictureformat_1bit

In this format, each bit represents a pixel (so one byte contains eight pixels). If the width is not divisible by eight, then the last bits of the last byte of the line are unused (fill bits), and the next line starts at the beginning of the next byte; this makes the navigation between lines easier, but takes up more space.

An off bit (0b0) represents a white pixel, and an on bit (0b1) represents a black pixel.

For calculating the size of such pictures, calculate the number of bytes a line occupies (usually ceil(w / 8)) and multiply it by the number of lines.

casio_pictureformat_1bit_r

Same as casio_pictureformat_1bit, except an off bit (0b0) represents a black pixel, and an on bit (0b1) represents a white pixel.

casio_pictureformat_1bit_packed

Packed monochrome pictures are basically the same as the format described for casio_pictureformat_1bit, except there are no fill bits: if a picture width is 6 pixels, then the second line will start at the seventh bit of the first byte (where it would start at the first bit of the second byte with fill bits).

The navigation to a line is less easy as it takes at least one division.

For calculating the size of such pictures, calculate the total number P of pixels (w * h) and divide it by the size of a byte (ceil(p / 8)).

casio_pictureformat_1bit_packed_r

Same as casio_pictureformat_1bit_packed, with the differences described in casio_pictureformat_1bit_r.

casio_pictureformat_1bit_old

The old monochrome format used by CASIO is basically a normal monochrome format (the width is usually 96 or 128, so no need for fill bits), except that it starts with the last byte (where the bits are in left to right), but it goes right to left, bottom to top.

The size is the same as for casio_pictureformat_1bit, except the byte order changes.

casio_pictureformat_2bit_dual

This is the format used for the Prizm’s projector mode. It is composed of two monochrome pictures (with sizes divisible by eight). It is basically gray pictures, with white, gray, dark gray and black.

To calculate the size, well, just multiply the size of such a picture in the casio_pictureformat_1bit per 2.

casio_pictureformat_4bit

This is a 4 bit per pixel format. There is no need for fill nibbles. Each nibble (group of 4 bits) is made of the following:

  • one bit for red (OR by 0xFF0000).

  • one bit for green (OR by 0x00FF00).

  • one bit for blue (OR by 0x0000FF).

  • one alignment bit.

To calculate the size, divide the number of pixels (w * h) by 2.

casio_pictureformat_4bit_code

In this encoding, each nibble for a pixel represents one of the colors defined in casio_colorcode_t or, in case of an illegal value (8 and above), plain black.

The size is calculated the same way as for casio_pictureformat_4bit.

casio_pictureformat_4bit_color

This format is used by old CASIO models. It is made of four monochrome pictures (no need for fill bits), where the palettes are orange, green, blue, white (bg).

To get the size, just multiply the size of a VRAM (see casio_pictureformat_1bit) by 4.

casio_pictureformat_4bit_mono

Same as casio_pictureformat_4bit_color, except the palette are (unused), (unused), black, white (bg).

casio_pictureformat_casemul

This format is used by CasEmul. It is basically arbitrary color codes, 1 byte per code, where, for example, 1 is orange. You can check the full color codes in lib/picture.c.

The size in bytes is the number of pixels.

casio_pictureformat_16bit

This format is used for the Prizm’s VRAM. Each pixel is two bytes long, where:

  • the first five bytes represents the high five (clap!) bits of the red part.

  • the next six bits represent the high six bits of the green part.

  • the last five bits represent the high five (re-clap!) bits of the blue part.

The size in bytes is the number of pixels times 2.

Managing a picture

You cannot make a picture directly, you have to decode it.

void casio_free_picture(casio_picture_t *picture)

Free the picture. Any related resource (such as the pixel matrix) will also be free’d, so be careful.

int casio_get_picture_dimensions(casio_picture_t *picture, unsigned int *widthp, unsigned int *heightp)

Get the picture width and height.

int casio_access_pixels(casio_picture_t *picture, casio_pixel_t ***pixels)

Access the pixels as a pixel matrix.

Encoding and decoding a picture

int casio_decode_picture(casio_picture_t **picturep, unsigned int width, unsigned int height, casio_pictureformat_t format, tio_stream_t *stream)

Create a picture out of a readable stream, with the width and height.

int casio_decode_picture_buffer(casio_picture_t **picturep, unsigned int width, unsigned int height, casio_pictureformat_t format, void const *data, size_t data_size)

Create a picture out of raw data, with the width and height.

int casio_get_picture_encoded_size(casio_picture_t *picture, casio_pictureformat_t format, size_t *sizep)

Get the required size for encoding the picture in a given format.

int casio_encode_picture(casio_picture_t *picture, casio_pictureformat_t format, void *buf, size_t size)

Get the encoded form of a picture, using a given format and encoding into the given buffer.