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.IX Title "PDF::Builder::Resource::XObject::Image::PNG 3pm"
.TH PDF::Builder::Resource::XObject::Image::PNG 3pm "2021-03-28" "perl v5.32.1" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.if n .ad l
.nh
.SH "NAME"
PDF::Builder::Resource::XObject::Image::PNG \- support routines for PNG image 
library (using pure Perl code). 
Inherits from PDF::Builder::Resource::XObject::Image
.SH "METHODS"
.IX Header "METHODS"
.ie n .IP "$res = PDF::Builder::Resource::XObject::Image::PNG\->new($pdf, $file, $name, %opts)" 4
.el .IP "\f(CW$res\fR = PDF::Builder::Resource::XObject::Image::PNG\->new($pdf, \f(CW$file\fR, \f(CW$name\fR, \f(CW%opts\fR)" 4
.IX Item "$res = PDF::Builder::Resource::XObject::Image::PNG->new($pdf, $file, $name, %opts)"
.PD 0
.ie n .IP "$res = PDF::Builder::Resource::XObject::Image::PNG\->new($pdf, $file, $name)" 4
.el .IP "\f(CW$res\fR = PDF::Builder::Resource::XObject::Image::PNG\->new($pdf, \f(CW$file\fR, \f(CW$name\fR)" 4
.IX Item "$res = PDF::Builder::Resource::XObject::Image::PNG->new($pdf, $file, $name)"
.ie n .IP "$res = PDF::Builder::Resource::XObject::Image::PNG\->new($pdf, $file)" 4
.el .IP "\f(CW$res\fR = PDF::Builder::Resource::XObject::Image::PNG\->new($pdf, \f(CW$file\fR)" 4
.IX Item "$res = PDF::Builder::Resource::XObject::Image::PNG->new($pdf, $file)"
.PD
.PP
Returns a PNG-image object. \f(CW$pdf\fR is the \s-1PDF\s0 object being added to, \f(CW$file\fR
is the input \s-1PNG\s0 file, and the optional \f(CW$name\fR of the new parent image object
defaults to PxAAA.
.PP
If the Image::PNG::Libpng package is installed, the \s-1PNG_IPL\s0 library will be
used instead of the \s-1PNG\s0 library. In such a case, use of the \s-1PNG\s0 library may be
forced via the \f(CW\*(C`\-nouseIPL\*(C'\fR flag (see Builder documentation for \f(CW\*(C`image_png()\*(C'\fR).
.PP
opts: \-notrans
.PP
.Vb 2
\&   No transparency \-\- ignore tRNS chunk if provided, ignore Alpha channel
\&   if provided.
.Ve
.SS "Supported \s-1PNG\s0 types"
.IX Subsection "Supported PNG types"
.Vb 5
\&   (0) Gray scale of depth 1, 2, 4, or 8 bits per pixel (2, 4, 16, or 256 
\&       gray levels). 16 bpp is not currently supported (a PNG with 16 bpp 
\&       is a fatal error). Full transparency (of one 8\-bit gray value) via 
\&       the tRNS chunk is allowed, unless the \-notrans option specifies 
\&       that it be ignored.
\&
\&   (2) RGB 24\-bit truecolor with 8 bits per sample (16.7 million colors). 
\&       16 bps is not currently supported (a PNG with 16 bps is a fatal 
\&       error). Full transparency (of one 3x8\-bit RGB color value) via the 
\&       tRNS chunk is allowed, unless the \-notrans option specifies that it 
\&       be ignored.
\&
\&   (3) Palette color with 1, 2, 4, or 8 bits per pixel (2, 4, 16, or 256
\&       color table/palette entries). 16 bpp is not currently supported by 
\&       PNG or PDF. Partial transparency (8\-bit Alpha) for each palette 
\&       entry via the tRNS chunk is allowed, unless the \-notrans option 
\&       specifies that it be ignored (all entries fully opaque).
\&
\&   (4) Gray scale of depth 8 bits per pixel plus 8\-bit Alpha channel (256
\&       gray levels and 256 levels of transparency). 16 bpp is not 
\&       currently supported (a PNG with 16 bpp is a fatal error). The Alpha 
\&       channel is ignored if the \-notrans option is given. The tRNS chunk 
\&       is not permitted.
\&
\&   (6) RGB 24\-bit truecolor with 8 bits per sample (16.7 million colors) 
\&       plus 8\-bit Alpha channel (256 levels of transparency). 16 bps is not 
\&       currently supported (a PNG with 16 bps is a fatal error). The Alpha 
\&       channel is ignored if the \-notrans option is given. The tRNS chunk 
\&       is not permitted.
.Ve
.PP
In all cases, 16 bits per sample are not implemented. A fatal error will be
returned if a \s-1PNG\s0 image with 16\-bps data is supplied. The code is assuming
standard \*(L"network\*(R" bit ordering (Big Endian). Interlaced (progressive) display
images are not supported. Use the \s-1PNG_IPL\s0 version if you need to support 16 bps
or interlaced images.
.PP
The transparency chunk (tRNS) will specify one gray level entry or one \s-1RGB\s0
entry to be treated as transparent (Alpha = 0). For palette color, up to 
256 palette entry 8\-bit Alpha values are specified (256 levels of transparency, 
from 0 = transparent to 255 = opaque).
.PP
Only a limited number of chunks are handled: \s-1IHDR, IDAT\s0 (internally), \s-1PLTE,\s0 
tRNS, and \s-1IEND\s0 (internally). All other chunks are ignored at this time. Certain 
filters and compressions applied to data will be handled, but there may be 
unsupported methods.
.ie n .IP "$mode = $png\->\fBusesLib()\fR" 4
.el .IP "\f(CW$mode\fR = \f(CW$png\fR\->\fBusesLib()\fR" 4
.IX Item "$mode = $png->usesLib()"
Returns 1 if Image::PNG::Libpng installed and used, 0 if not installed, or \-1 
if installed but not used (\-nouseIPL option given to \f(CW\*(C`image_png\*(C'\fR).
.Sp
\&\fBCaution:\fR this method can only be used \fIafter\fR the image object has been
created. It can't tell you whether Image::PNG::Libpng is available in
advance of actually using it, in case you want to use some functionality
available only in \s-1PNG_IPL.\s0 See the PDF::Builder \s-1\fBLA_IPL\s0()\fR call if you
need to know in advance.