=head1 NAME Imager::Files - working with image files =head1 SYNOPSIS my $img = ...; $img->write(file=>$filename, type=>$type) or die "Cannot write: ",$img->errstr; $img = Imager->new; $img->read(file=>$filename, type=>$type) or die "Cannot read: ", $img->errstr; Imager->write_multi({ file=> $filename, ... }, @images) or die "Cannot write: ", Imager->errstr; my @imgs = Imager->read_multi(file=>$filename) or die "Cannot read: ", Imager->errstr; =head1 DESCRIPTION You can read and write a variety of images formats, assuming you have the appropriate libraries, and images can be read or written to/from files, file handles, file descriptors, scalars, or through callbacks. To see which image formats Imager is compiled to support the following code snippet is sufficient: use Imager; print join " ", keys %Imager::formats; This will include some other information identifying libraries rather than file formats. Reading writing to and from files is simple, use the C method to read an image: my $img = Imager->new; $img->read(file=>$filename, type=>$type) or die "Cannot read $filename: ", $img->errstr; and the C method to write an image: $img->write(file=>$filename, type=>$type) or die "Cannot write $filename: ", $img->errstr; If you're reading from a format that supports multiple images per file, use the C method: my @imgs = Imager->read_multi(file=>$filename, type=>$type) or die "Cannot read $filename: ", Imager->errstr; and if you want to write multiple images to a single file use the C method: Imager->write_multi({ file=> $filename, type=>$type }, @images) or die "Cannot write $filename: ", Imager->errstr; If the I includes an extension that Imager recognizes, then you don't need the I, but you may want to provide one anyway. See L for information on controlling this recognition. The C parameter is a lowercase representation of the file type, and can be any of the following: bmp Windows BitMaP (BMP) gif Graphics Interchange Format (GIF) jpeg JPEG/JFIF png Portable Network Graphics (PNG) pnm Portable aNyMap (PNM) raw Raw rgb SGI .rgb files tga TARGA tiff Tagged Image File Format (TIFF) When you read an image, Imager may set some tags, possibly including information about the spatial resolution, textual information, and animation information. See L for specifics. =head2 Input and output When reading or writing you can specify one of a variety of sources or targets: =over =item file The C parameter is the name of the image file to be written to or read from. If Imager recognizes the extension of the file you do not need to supply a C. =item fh C is a file handle, typically either returned from C<new()>>, or a glob from an C call. You should call C on the handle before passing it to Imager. Imager will set the handle to autoflush to make sure any buffered data is flushed , since Imager will write to the file descriptor (from fileno()) rather than writing at the perl level. =item fd C is a file descriptor. You can get this by calling the C function on a file handle, or by using one of the standard file descriptor numbers. If you get this from a perl file handle, you may need to flush any buffered output, otherwise it may appear in the output stream after the image. =item data When reading data, C is a scalar containing the image file data, when writing, C is a reference to the scalar to save the image file data too. For GIF images you will need giflib 4 or higher, and you may need to patch giflib to use this option for writing. =item callback Imager will make calls back to your supplied coderefs to read, write and seek from/to/through the image file. When reading from a file you can use either C or C to supply the read callback, and when writing C or C to supply the write callback. When writing you can also supply the C option to set the maximum amount of data that will be buffered before your write callback is called. Note: the amount of data supplied to your callback can be smaller or larger than this size. The read callback is called with 2 parameters, the minimum amount of data required, and the maximum amount that Imager will store in it's C level buffer. You may want to return the minimum if you have a slow data source, or the maximum if you have a fast source and want to prevent many calls to your perl callback. The read data should be returned as a scalar. Your write callback takes exactly one parameter, a scalar containing the data to be written. Return true for success. The seek callback takes 2 parameters, a I, and a I, defined in the same way as perl's seek function. You can also supply a C which is called with no parameters when there is no more data to be written. This could be used to flush buffered data. =back =head2 Guessing types Imager uses the code reference in $Imager::FORMATGUESS to guess the file type when you don't supply a C. The code reference is called with a single parameter, the filename of the file. The code reference is only called if a C parameter is supplied to the file access method. Return either a valid Imager file type, or undef. # I'm writing jpegs to weird filenames local $Imager::FORMATGUESS = sub { 'jpeg' }; =head1 TYPE SPECIFIC INFORMATION The different image formats can write different image type, and some have different options to control how the images are written. When you call C or C with an option that has the same name as a tag for the image format you're writing, then the value supplied to that option will be used to set the corresponding tag in the image. Depending on the image format, these values will be used when writing the image. This replaces the previous options that were used when writing GIF images. Currently if you use an obsolete option, it will be converted to the equivalent tag and Imager will produced a warning. You can suppress these warnings by calling the C function with the C option set to false: Imager::init(warn_obsolete=>0); At some point in the future these obsolete options will no longer be supported. =head2 PNM (Portable aNy Map) Imager can write PGM (Portable Gray Map) and PPM (Portable PixMaps) files, depending on the number of channels in the image. Currently the images are written in binary formats. Only 1 and 3 channel images can be written, including 1 and 3 channel paletted images. $img->write(file=>'foo.ppm') or die $img->errstr; Imager can read both the ASCII and binary versions of each of the PBM (Portable BitMap), PGM and PPM formats. $img->read(file=>'foo.ppm') or die $img->errstr; PNM does not support the spatial resolution tags. =head2 JPEG You can supply a C parameter (0-100) when writing a JPEG file, which defaults to 75%. Only 1 and 3 channel images can be written, including 1 and 3 channel paletted images. $img->write(file=>'foo.jpg', jpegquality=>90) or die $img->errstr; Imager will read a grayscale JPEG as a 1 channel image and a color JPEG as a 3 channel image. $img->read(file=>'foo.jpg') or die $img->errstr; PNM does not support the spatial resolution tags. =head2 GIF (Graphics Interchange Format) When writing one of more GIF images you can use the same L as you can when converting an RGB image into a paletted image. When reading a GIF all of the sub-images are combined using the screen size and image positions into one big image, producing an RGB image. This may change in the future to produce a paletted image where possible. When you read a single GIF with C<$img-Eread()> you can supply a reference to a scalar in the C parameter, if the image is read the scalar will be filled with a reference to an anonymous array of L objects, representing the palette of the image. This will be the first palette found in the image. If you want the palettes for each of the images in the file, use C and use the C method on each image. GIF does not support the spatial resolution tags. Imager will set the following tags in each image when reading, and can use most of them when writing to GIF: =over =item gif_left the offset of the image from the left of the "screen" ("Image Left Position") =item gif_top the offset of the image from the top of the "screen" ("Image Top Position") =item gif_interlace non-zero if the image was interlaced ("Interlace Flag") =item gif_screen_width =item gif_screen_height the size of the logical screen. When writing this is used as the minimum. If any image being written would extend beyond this the screen size is extended. ("Logical Screen Width", "Logical Screen Height"). When writing this is used as a minimum, if the combination of the image size and the image's C and C is beyond this size then the screen size will be expanded. =item gif_local_map Non-zero if this image had a local color map. If set for an image when writing the image is quantized separately from the other images in the file. =item gif_background The index in the global colormap of the logical screen's background color. This is only set if the current image uses the global colormap. You can set this on write too, but for it to choose the color you want, you will need to supply only paletted images and set the C tag to 0. =item gif_trans_index The index of the color in the colormap used for transparency. If the image has a transparency then it is returned as a 4 channel image with the alpha set to zero in this palette entry. This value is not used when writing. ("Transparent Color Index") =item gif_trans_color A reference to an Imager::Color object, which is the colour to use for the palette entry used to represent transparency in the palette. You need to set the transp option (see L) for this value to be used. =item gif_delay The delay until the next frame is displayed, in 1/100 of a second. ("Delay Time"). =item gif_user_input whether or not a user input is expected before continuing (view dependent) ("User Input Flag"). =item gif_disposal how the next frame is displayed ("Disposal Method") =item gif_loop the number of loops from the Netscape Loop extension. This may be zero. =item gif_comment the first block of the first gif comment before each image. =item gif_eliminate_unused If this is true, when you write a paletted image any unused colors will be eliminated from its palette. This is set by default. =back Where applicable, the ("name") is the name of that field from the GIF89 standard. The following gif writing options are obsolete, you should set the corresponding tag in the image, either by using the tags functions, or by supplying the tag and value as options. =over =item gif_each_palette Each image in the gif file has it's own palette if this is non-zero. All but the first image has a local colour table (the first uses the global colour table. Use C in new code. =item interlace The images are written interlaced if this is non-zero. Use C in new code. =item gif_delays A reference to an array containing the delays between images, in 1/100 seconds. Use C in new code. =item gif_positions A reference to an array of references to arrays which represent screen positions for each image. New code should use the C and C tags. =item gif_loop_count If this is non-zero the Netscape loop extension block is generated, which makes the animation of the images repeat. This is currently unimplemented due to some limitations in giflib. =back =head2 TIFF (Tagged Image File Format) Imager can write images to either paletted or RGB TIFF images, depending on the type of the source image. Currently if you write a 16-bit/sample or double/sample image it will be written as an 8-bit/sample image. Only 1 or 3 channel images can be written. If you are creating images for faxing you can set the I parameter set to C. By default the image is written in fine mode, but this can be overridden by setting the I parameter to zero. Since a fax image is bi-level, Imager uses a threshold to decide if a given pixel is black or white, based on a single channel. For greyscale images channel 0 is used, for color images channel 1 (green) is used. If you want more control over the conversion you can use $img->to_paletted() to product a bi-level image. This way you can use dithering: my $bilevel = $img->to_paletted(colors=>[ NC(0,0,0), NC(255,255,255) ], make_colors => 'none', translate => 'errdiff', errdiff => 'stucki'); =over =item class If set to 'fax' the image will be written as a bi-level fax image. =item fax_fine By default when I is set to 'fax' the image is written in fine mode, you can select normal mode by setting I to 0. =back Imager should be able to read any TIFF image you supply. Paletted TIFF images are read as paletted Imager images, since paletted TIFF images have 16-bits/sample (48-bits/color) this means the bottom 8-bits are lost, but this shouldn't be a big deal. Currently all direct color images are read at 8-bits/sample. TIFF supports the spatial resolution tags. See the C tag for some extra options. The following tags are set in a TIFF image when read, and can be set to control output: =over =item tiff_resolutionunit The value of the ResolutionUnit tag. This is ignored on writing if the i_aspect_only tag is non-zero. The C and C tags are expressed in pixels per inch no matter tha value of this tag, they will be converted to/from the value stored in the TIFF file. =item tiff_resolutionunit_name This is set when reading a TIFF file to the name of the unit given by C. Possible results include C, C, C (the C tag is also set reading these files) or C. =item tiff_documentname =item tiff_imagedescription =item tiff_make =item tiff_model =item tiff_pagename =item tiff_software =item tiff_datetime =item tiff_artist =item tiff_hostcomputer Various strings describing the image. tiff_datetime must be formatted as "YYYY:MM:DD HH:MM:SS". These correspond directly to the mixed case names in the TIFF specification. These are set in images read from a TIFF and saved when writing a TIFF image. =back =head2 BMP (BitMaP) Imager can write 24-bit RGB, and 8, 4 and 1-bit per pixel paletted Windows BMP files. Currently you cannot write compressed BMP files with Imager. Imager can read 24-bit RGB, and 8, 4 and 1-bit perl pixel paletted Windows BMP files. There is some support for reading 16-bit per pixel images, but I haven't found any for testing. BMP has no support for multi-image files. BMP files support the spatial resolution tags, but since BMP has no support for storing only an aspect ratio, if C is set when you write the C and C values are scaled so the smaller it 72 DPI. The following tags are set when you read an image from a BMP file: =over =item bmp_compression The type of compression, if any. This can be any of the following values: =over =item BI_RGB (0) Uncompressed. =item BI_RLE8 (1) 8-bits/pixel paletted value RLE compression. =item BI_RLE4 (2) 4-bits/pixel paletted value RLE compression. =item BI_BITFIELDS (3) Packed RGB values. =back =item bmp_compression_name The bmp_compression value as a BI_* string =item bmp_important_colors The number of important colors as defined by the writer of the image. =item bmp_used_colors Number of color used from the BMP header =item bmp_filesize The file size from the BMP header =item bmp_bit_count Number of bits stored per pixel. (24, 8, 4 or 1) =back =head2 TGA (TarGA) When storing targa images rle compression can be activated with the 'compress' parameter, the 'idstring' parameter can be used to set the targa comment field and the 'wierdpack' option can be used to use the 15 and 16 bit targa formats for rgb and rgba data. The 15 bit format has 5 of each red, green and blue. The 16 bit format in addition allows 1 bit of alpha. The most significant bits are used for each channel. Tags: =over =item tga_idstring =item tga_bitspp =item compressed =back =head2 RAW When reading raw images you need to supply the width and height of the image in the xsize and ysize options: $img->read(file=>'foo.raw', xsize=>100, ysize=>100) or die "Cannot read raw image\n"; If your input file has more channels than you want, or (as is common), junk in the fourth channel, you can use the datachannels and storechannels options to control the number of channels in your input file and the resulting channels in your image. For example, if your input image uses 32-bits per pixel with red, green, blue and junk values for each pixel you could do: $img->read(file=>'foo.raw', xsize=>100, ysize=>100, datachannels=>4, storechannels=>3) or die "Cannot read raw image\n"; Normally the raw image is expected to have the value for channel 1 immediately following channel 0 and channel 2 immediately following channel 1 for each pixel. If your input image has all the channel 0 values for the first line of the image, followed by all the channel 1 values for the first line and so on, you can use the interleave option: $img->read(file=>'foo.raw', xsize=100, ysize=>100, interleave=>1) or die "Cannot read raw image\n"; =head2 PNG There are no PNG specific tags. =head1 EXAMPLES =head2 Producing an image from a CGI script Once you have an image the basic mechanism is: =over =item 1. set STDOUT to autoflush =item 2. output a content-type header, and optionally a content-length header =item 3. put STDOUT into binmode =item 4. call write() with the C or C parameter. You will need to provide the C parameter since Imager can't use the extension to guess the file format you want. =back # write an image from a CGI script # using CGI.pm use CGI qw(:standard); $| = 1; binmode STDOUT; print header(-type=>'image/gif'); $img->write(type=>'gif', fd=>fileno(STDOUT)) or die $img->errstr; If you want to send a content length you can send the output to a scalar to get the length: my $data; $img->write(type=>'gif', data=>\$data) or die $img->errstr; binmode STDOUT; print header(-type=>'image/gif', -content_length=>length($data)); print $data; =head2 Writing an animated GIF The basic idea is simple, just use write_multi(): my @imgs = ...; Imager->write_multi({ file=>$filename, type=>'gif' }, @imgs); If your images are RGB images the default quantization mechanism will produce a very good result, but can take a long time to execute. You could either use the standard webmap: Imager->write_multi({ file=>$filename, type=>'gif', make_colors=>'webmap' }, @imgs); or use a median cut algorithm to built a fairly optimal color map: Imager->write_multi({ file=>$filename, type=>'gif', make_colors=>'mediancut' }, @imgs); By default all of the images will use the same global colormap, which will produce a smaller image. If your images have significant color differences, you may want to generate a new palette for each image: Imager->write_multi({ file=>$filename, type=>'gif', make_colors=>'mediancut', gif_local_map => 1 }, @imgs); which will set the C tag in each image to 1. Alternatively, if you know only some images have different colors, you can set the tag just for those images: $imgs[2]->settag(name=>'gif_local_map', value=>1); $imgs[4]->settag(name=>'gif_local_map', value=>1); and call write_multi() without a C parameter, or supply an arrayref of values for the tag: Imager->write_multi({ file=>$filename, type=>'gif', make_colors=>'mediancut', gif_local_map => [ 0, 0, 1, 0, 1 ] }, @imgs); Other useful parameters include C to control the delay between frames and C to control transparency. =head2 Reading tags after reading an image This is pretty simple: # print the author of a TIFF, if any my $img = Imager->new; $img->read(file=>$filename, type='tiff') or die $img->errstr; my $author = $img->tags(name=>'tiff_author'); if (defined $author) { print "Author: $author\n"; } =head1 BUGS When saving Gif images the program does NOT try to shave of extra colors if it is possible. If you specify 128 colors and there are only 2 colors used - it will have a 128 colortable anyway. =head1 SEE ALSO Imager(3) =cut