Implements read_image and write_image functions. More...

Detailed Description

Implements read_image and write_image functions.

Author: Pascal Getreuer getre.nosp@m.uer@.nosp@m.cmla..nosp@m.ens-.nosp@m.cacha.nosp@m.n.fr

This program is free software: you can redistribute it and/or modify it under, at your option, the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version, or the terms of the simplified BSD license.

You should have received a copy of these licenses along this program. If not, see http://www.gnu.org/licenses/ and http://www.opensource.org/licenses/bsd-license.html.

Definition in file imageio.h.

#include <stdio.h>
#include "basic.h"

Go to the source code of this file.

Macros
#define	MAX_IMAGE_SIZE 10000
	Limit on the maximum allowed image width or height (security).

#define	READIMAGE_FORMATS_SUPPORTED "BMP" SUPPORTEDSTRING_JPEG SUPPORTEDSTRING_PNG SUPPORTEDSTRING_TIFF
	String macro listing supported formats for `ReadImage`. More...

#define	WRITEIMAGE_FORMATS_SUPPORTED "BMP" SUPPORTEDSTRING_JPEG SUPPORTEDSTRING_PNG SUPPORTEDSTRING_TIFF
	String macro listing supported formats for `WriteImage`.

#define	_CRT_SECURE_NO_WARNINGS
	Avoid MSVC warnings on using fopen.

Functions
int	identify_image_type (char type, const char filename)
	Identify the file type of an image file by its magic numbers. More...

void *	read_image (int width, int height, const char *filename, unsigned format)
	Read an image file as 32-bit RGBA data. More...

int	write_image (void image, int width, int height, const char filename, unsigned format, int quality)
	Write an image file from 8-bit RGBA image data. More...

Macro Definition Documentation

#define READIMAGE_FORMATS_SUPPORTED "BMP" SUPPORTEDSTRING_JPEG SUPPORTEDSTRING_PNG SUPPORTEDSTRING_TIFF

String macro listing supported formats for ReadImage.

This macro can be used for example as

printf("Supported formats for reading: " READIMAGE_FORMATS_SUPPORTED ".\n");

Definition at line 79 of file imageio.h.

Function Documentation

int identify_image_type	(	char *	type,
		const char *	filename
	)

Identify the file type of an image file by its magic numbers.

Parameters

type	destination buffer with space for at least 5 chars
filename	image file name

Returns: 1 on successful identification, 0 on failure.

The routine fills type with an identifying string. If there is an error or the file type is unknown, type is set to a null string.

Definition at line 1955 of file imageio.c.

void* read_image	(	int *	width,
		int *	height,
		const char *	filename,
		unsigned	format
	)

Read an image file as 32-bit RGBA data.

Parameters

width,height	pointers to be filled with the image dimensions
filename	image file name
format	specifies the desired format for the image

Returns: Pointer to the image data, or null on failure

The calling syntax is that the filename is the input and width, and height and the returned pointer are outputs. read_image allocates memory for the image as one contiguous block of memory and returns a pointer. It is the responsibility of the caller to call free on this pointer when done to release this memory.

A non-null pointer indicates success. On failure, the returned pointer is null, and width and height are set to 0.

The format argument is used by specifying one of the data type options

IMAGEIO_U8: unsigned 8-bit components
IMAGEIO_SINGLE: float components
IMAGEIO_DOUBLE: double components

and one of the channel options

IMAGEIO_GRAYSCALE: grayscale data
IMAGEIO_RGB: RGB color data (red is the first channel)
IMAGEIO_BGR: BGR color data (blue is the first channel)
IMAGEIO_RGBA: RGBA color+alpha data
IMAGEIO_BGRA: BGRA color+alpha data
IMAGEIO_ARGB: ARGB color+alpha data
IMAGEIO_ABGR: ABGR color+alpha data

and optionally either or both of the ordering options

IMAGEIO_PLANAR: planar order instead of interleaved components
IMAGEIO_COLUMNMAJOR: column major order instead of row major order

uint32_t *image;
int width, height;
if (!(image = (uint32_t *)read_image(&width, &height, "myimage.bmp",
    IMAGEIO_U8 | IMAGEIO_RGBA)))
    return 0;
printf("Read image of size %dx%d\n", width, height);
...
free(image);

With the default formatting IMAGEIO_U8 | IMAGEIO_RGBA, the image is organized in standard row major top-down 32-bit RGBA order. The image is organized as

    (Top left)                                             (Top right)
    image[0]                image[1]        ...  image[width-1]
    image[width]            image[width+1]  ...  image[2*width]
    ...                     ...             ...  ...
    image[width*(height-1)] ...             ...  image[width*height-1]
    (Bottom left)                                       (Bottom right)

Each element image[k] represents one RGBA pixel, which is a 32-bit bitfield. The components of pixel image[k] can be unpacked as

uint8_t *Component = (uint8_t *)&image[k];
uint8_t red = Component[0];
uint8_t green = Component[1];
uint8_t blue = Component[2];
uint8_t alpha = Component[3];

Each component is an unsigned 8-bit integer value with range 0-255. Most images do not have alpha information, in which case the alpha component is set to value 255 (full opacity).

With IMAGEIO_SINGLE or IMAGEIO_DOUBLE, the components are values in the range 0 to 1.

Definition at line 2083 of file imageio.c.

int write_image	(	void *	image,
		int	width,
		int	height,
		const char *	filename,
		unsigned	format,
		int	quality
	)

Write an image file from 8-bit RGBA image data.

Parameters

image	pointer to the image data
width,height	image dimensions
filename	image file name
format	specifies how the data is formatted (see read_image)
quality	the JPEG image quality (between 0 and 100)

Returns: 1 on success, 0 on failure

The input image should be a 32-bit RGBA image stored as in the description of read_image. write_image writes to filename in the file format specified by its extension. If saving a JPEG image, the quality argument specifies the quality factor (between 0 and 100). quality has no effect on other formats.

The return value indicates success with 1 or failure with 0.

Definition at line 2188 of file imageio.c.

Detailed Description

Macros

Functions

Macro Definition Documentation

Function Documentation