Hossin-Azmoud/C-Image

PNG image manipulation in C/Python from scratch.

C-Image

Image manipulation scripts and function in C/python.

Constants and enums

1. The Official PNG signiture to identify valid PNG Image.

static const uint8_t PNG_SIG[PNG_SIG_CAP] = {
	137, 
	80, 
	78, 
	71, 
	13, 
	10, 
	26, 
	10
}; 

2. chunk types to identify the chunks.

typedef enum CHUNK_TYPES {
	IEND_ = 0x444E4549, 
	IHDR_ = 0x52444849,
	IDAT_ = 0x54414449,
} CHUNK_TYPE;

3. Default capacities for reading bytes.

#define TYPE_CAP     4
#define CHUNK_SIZE   1024
#define PNG_SIG_CAP  8

4. Enum Format for print functions (print as hex, ascii or integer).

typedef enum Format {
	HEX = 0,
	ASCII,
	INT,
} Format;
 

structures

1. structure to parse an individual chunk from a stream.

typedef struct PNGChunk 
{   
	uint32_t length; 
	uint8_t  type[TYPE_CAP];
	uint32_t data[CHUNK_SIZE];
	uint32_t crc;

} Chunk; 

2. structure to decode an IHDR chunk.

typedef struct IHDR {
	uint32_t Width, Height; 
   	uint8_t BitDepth;
   	uint8_t ColorType;
   	uint8_t CompressionMethod;
   	uint8_t FilterMethod;
   	uint8_t InterlaceMethod;
} IHDR;

Functions

• print_byte(uint8_t byte, Format f): Print a byte with specified format (HEX, ASCII, INT).
• print_as(const char *Label, uint8_t *buffer, size_t cap, Format f): print a buffer with specified format (HEX, ASCII, INT)
• read_bytes(FILE *Stream, void *buff, size_t buff_cap): Load buff_cap bytes from stream into buff, on failure quit.
• reverse_bytes(void *buf0, size_t buf_cap): reverse bytes (because 32bit integers as stored in opposite order)
• *ReadIHDR(FILE *Stream): read then return IHDR structure from png file stream.
• PrintIHDR(IHDR *ihdr): print IHDR chunk.
• report_chunk(Chunk *C): report a given chunk's info.
• *ReadChunk(FILE *Stream, IHDR *ihdr): read a chunk and if it is IHDR, Store its data in IHDR structure.
• ReadIntoChunkBuffer(FILE *Stream, Chunk *CBuffer): Read a chunk into a preallocated buffer.

resources

Official Png format: libpng docs