Imager's per-thread context.

Represents a slot in the context object.

A signed integer type that represents an image dimension or ordinate.

May be larger than int on some platforms.

An unsigned variant of "i_img_dim".

Type for 8-bit/sample color.

Samples as per;

i_color c;

i_color is a union of:

• gray - contains a single element gray_color, eg. c.gray.gray_color

• rgb - contains three elements r, g, b, eg. c.rgb.r

• rgba - contains four elements r, g, b, a, eg. c.rgba.a

• cmyk - contains four elements c, m, y, k, eg. c.cmyk.y. Note that Imager never uses CMYK colors except when reading/writing files.

• channels - an array of four channels, eg c.channels[2].

This is the double/sample color type.

Its layout exactly corresponds to i_color.

This is Imager's image type.

It contains the following members:

• channels - the number of channels in the image

• xsize, ysize - the width and height of the image in pixels

• bytes - the number of bytes used to store the image data. Undefined where virtual is non-zero.

• ch_mask - a mask of writable channels. eg. if this is 6 then only channels 1 and 2 are writable. There may be bits set for which there are no channels in the image.

• bits - the number of bits stored per sample. Should be one of i_8_bits, i_16_bits, i_double_bits.

• type - either i_direct_type for direct color images, or i_palette_type for paletted images.

• isvirtual - if zero then this image is-self contained. If non-zero then this image could be an interface to some other implementation.

• idata - the image data. This should not be directly accessed. A new image implementation can use this to store its image data. i_img_destroy() will myfree() this pointer if it's non-null.

• tags - a structure storing the image's tags. This should only be accessed via the i_tags_*() functions.

• ext_data - a pointer for use internal to an image implementation. This should be freed by the image's destroy handler.

• im_data - data internal to Imager. This is initialized by i_img_init().

• i_f_ppix, i_f_ppixf, i_f_plin, i_f_plinf, i_f_gpix, i_f_gpixf, i_f_glin, i_f_glinf, i_f_gsamp, i_f_gampf - implementations for each of the required image functions. An image implementation should initialize these between calling i_img_alloc() and i_img_init().

• i_f_gpal, i_f_ppal, i_f_addcolors, i_f_getcolors, i_f_colorcount, i_f_maxcolors, i_f_findcolor, i_f_setcolors - implementations for each paletted image function.

• i_f_destroy - custom image destruction function. This should be used to release memory if necessary.

• i_f_gsamp_bits - implements i_gsamp_bits() for this image.

• i_f_psamp_bits - implements i_psamp_bits() for this image.

• i_f_psamp - implements psamp() for this image.

• i_f_psampf - implements psamp() for this image.

• im_data - image specific data internal to Imager.

• context - the Imager API context this image belongs to.

Represents a polygon. Has the following members:

• x, y - arrays of x and y locations of vertices.

• count - the number of entries in the x and y arrays.

Control how polygons are filled. Has the following values:

• i_pfm_evenodd - simple even-odd fills.

• i_pfm_nonzero - non-zero winding rule fills.

This is the "abstract" base type for Imager's fill types.

Unless you're implementing a new fill type you'll typically treat this as an opaque type.

Opaque type for Imager's mutex API.

An enumerated type for controlling how transparency is handled during quantization.

This has the following possible values:

• tr_none - ignore the alpha channel

• tr_threshold - simple transparency thresholding.

• tr_errdiff - use error diffusion to control which pixels are transparent.

• tr_ordered - use ordered dithering to control which pixels are transparent.

An enumerated type used to control the method used for produce the color map:

• mc_none - the user supplied map is used.

• mc_web_map - use the classic web map. Any existing fixed colors are ignored.

• mc_median_cut - use median cut

• mono - use a fixed black and white map.

• gray - 256 step gray map.

• gray4 - 4 step gray map.

• gray16 - 16 step gray map.

An enumerated type that controls how colors are translated:

• pt_giflib - obsolete, forces make_colors to use median cut and acts like pt_closest.

• pt_closest - always use the closest color.

• pt_perturb - add random values to each sample and find the closest color.

• pt_errdiff - error diffusion dither.

Controls the type of error diffusion to use:

• ed_floyd - floyd-steinberg

• ed_jarvis - Jarvis, Judice and Ninke

• ed_stucki - Stucki

• ed_custom - not usable for transparency dithering, allows a custom error diffusion map to be used.

• ed_bidir - or with the error diffusion type to use alternate directions on each line of the dither.

Which ordered dither map to use, currently only available for transparency. Values are:

• od_random - a pre-generated random map.

• od_dot8 - large dot dither.

• od_dot4 - smaller dot dither

• od_hline - horizontal line dither.

• od_vline - vertical line dither.

• od_slashline - / line dither.

• od_backline - \ line dither.

• od_tiny - small checkbox dither

• od_custom - custom dither map.

A structure type used to supply image quantization, ie. when converting a direct color image to a paletted image.

This has the following members:

• transp - how to handle transparency, see "i_transp".

• threshold - when transp is tr_threshold, this is the alpha level at which pixels become transparent.

• tr_errdiff - when transp is tr_errdiff this controls the type of error diffusion to be done. This may not be ed_custom for this member.

• tr_orddith - when transp is tr_ordered this controls the patten used for dithering transparency.

• tr_custom - when tr_orddith is tr_custom this is the ordered dither mask.

• make_colors - the method used to generate the color palette, see "i_make_colors".

• mc_colors - an array of mc_size "i_color" entries used to define the fixed colors (controlled by mc_count and to return the generated color list.

• mc_size - the size of the buffer allocated to mc_colors in sizeof(i_color) units.

• mc_count - the number of initialized colors in mc_colors.

• translate - how RGB colors are translated to palette indexes, see "i_translate".

• errdiff - when translate is pt_errdiff this controls the type of error diffusion to be done.

• ed_map, ed_width, ed_height, ed_orig - when errdiff is ed_custom this controls the error diffusion map. ed_map is an array of ed_width * ed_height integers. ed_orig is the position of the current pixel in the error diffusion map, always on the top row.

• perturb - the amount to perturb pixels when translate is mc_perturb.

Returned by "i_img_color_model(im)" to indicate the color model of the image.

An enumerated type with the following possible values:

• icm_unknown - the image has no usable color data. In future versions of Imager this will be returned in a few limited cases, eg. when the source image is CMYK and the user has requested no color translation is done.

• icm_gray - gray scale with no alpha channel.

• icm_gray_alpha - gray scale with an alpha channel.

• icm_rgb - RGB

• icm_rgb_alpha - RGB with an alpha channel.

This is a constant string that can be used with functions like printf() to format i_img_dim values after they're been cast with i_DFc().

Does not include the leading %.

Cast an i_img_dim value to a type for use with the i_DF format string.

Format a pair of i_img_dim values. This format string does include the leading %.

Casts two i_img_dim values for use with the i_DF (or i_DFp) format.