enhancements to the memory usage and template system of zend pdf?
Thanks!
Willie Alberty wrote:
>
> For the last few months I have been working with Kevin McArthur on a
> comprehensive PDF generation project for a client [Streamflow] who has
> some pretty advanced layout needs. The project is nearing completion
> and we have been discussing the possibility of contributing large
> portions of the code back to the Zend Framework as improvements to
> Zend_Pdf.
>
> In light of several recent postings to fw-general and fw-formats, as
> well as a few encouraging proposals recently submitted to the Wiki, we
> would like to formally announce our plans and describe the new
> functionality at a high level here.
>
> We will be submitting proposals in the coming weeks that describe
> these new components in more detail along with fully-functional
> reference implementations. Our hope is to join forces with other
> interested developers to help fast-track these proposals through the
> feedback and approval process, write tests, user documentation, and
> examples, and exercise the code as much as possible.
>
> We're really proud of this work and are excited to share it with the
> community. We believe that these enhancements will further establish
> Zend_Pdf's role as the gold standard for PDF generation using PHP.
>
>
> Text Layout Engine
> ------------------
>
> "How do I wrap long lines of text?" This is probably the most commonly-
> asked question regarding Zend_Pdf. I'm pleased to report that not only
> have we solved the problem of text-wrapping, but a whole host of
> others as well. The new engine provides fully-automatic text layout,
> and has customization hooks in a variety of places.
>
> Line breaks are calculated using the Unicode Line Breaking Algorithm
> (UAX #14), providing linguistically-appropriate line breaks, not just
> at whitespace characters.
>
> Paragraph styles allow you to specify left-, center-, and right-
> alignment, as well as full justification, line leading, line height,
> line multiple (double-space, triple-space, etc.), pre- and post-
> paragraph spacing, left- and right-side margins, and first-line
> indentation. Paragraph styles also support left-, center-, right-, and
> decimal-aligned tab stops, with or without leaders, for intra-line
> alignment needs.
>
> In addition to the left-to-right line sweep used by most Latin-based
> scripts, right-to-left line sweep is also supported, and is
> automatically detected by the layout engine; you never need to supply
> strings in reverse character order for right-to-left text layout.
>
> The layout engine is based around the concept of an attributed string.
> These are Unicode strings of unlimited length, and fully support the
> entire Unicode character set, including characters outside the Basic
> Multilingual Plane (BMP).
>
> Attributed strings allow you to assign stylistic attributes to
> arbitrary ranges of characters within the string. These attributes are
> used by typesetters to determine the specific look and location for
> every character. This means that you can make unlimited style changes
> within a block of text, even changing styles character-by-character if
> desired.
>
> The layout engine automatically manages all of these style changes,
> applying them as necessary when drawing the text on the page. The
> following style attributes are supported:
>
> - Font
> - Font size
> - Fill color
> - Stroke width and color
> - Underline and strikethrough
> - Super- and sub-script
> - Background color
>
> You can add your own custom attributes as well, which you can use in
> your own subclasses to completely customize the layout engine's
> behavior.
>
> These attributed strings will eventually be shared with Zend_Rtf
> (recently proposed by Andries Seutens), as each attributed string is
> essentially a self-contained RTF document. This opens up the
> possibility for generating fully-styled PDF or RTF output from the
> same source with only a couple of lines of code. It will also
> eventually be possible to use existing styled RTF documents as the
> basis for PDF text drawing, eliminating the need to manually apply
> style attributes in your PHP code.
>
> A layout manager class is responsible for drawing these attributed
> strings. It lays out the text in a series of arbitrarily-shaped text
> containers, automatically moving from one to the next as each is
> filled. Rectangular and circular containers will be provided, but you
> can easily create your own custom containers for other shapes or to
> flow text around images.
>
> Multi-column output is as easy as creating two adjacent text
> containers on the same page. Text containers don't even need to be on
> the same PDF page: you can start your text in a small container on
> page 1, then continue it on page 17.
>
> Callback functions are provided to allow you to create text additional
> containers as needed, which can be located on new pages. This is
> useful if you do not know the length of the text you are drawing ahead
> of time, or if you want to adapt your layout on-the-fly.
>
> You can also use multiple layout managers on a single page, allowing
> you to create complex multi-page flows for a series of text runs.
> These can be useful for creating page headers and footers, or for
> running stories side-by-side in a newsletter.
>
>
> Drawing Model
> -------------
>
> Three new primitive geometry classes allow you to precisely define
> drawing locations, sizes, and regions. They also provide a host of
> convenience functions allowing for calculation, conversion,
> intersection testing, etc.:
>
> - Point: x and y coordinate
> - Size: height and width
> - Rectangle: combination of a point and size
>
> PDF pages are drawn using a series of content streams, which contain
> all of the low-level drawing commands. Zend_Pdf_Page currently manages
> its own private content stream.
>
> We've separated content streams from Zend_Pdf_Page, promoting them to
> first-class objects. This allows us to use these content streams as
> templates that can be reused again and again, either on a single page
> or multiple pages. Templates can greatly reduce PDF file sizes and
> improve memory use and performance in PDF viewer applications.
>
> It is also possible to create a template from any page in an existing
> PDF document. You can then reuse the template in the same PDF, or even
> copy it to a new PDF document, where you can use it as a page
> background, draw it as a thumbnail, perform imposition, etc.
>
>
> Performance and Memory
> ----------------------
>
> We've also made numerous performance and memory-usage improvements
> throughout the code. Most data is now lazily-loaded, allowing you to
> manipulate very large documents, containing thousands or millions of
> individual objects or hundreds of megabytes or gigabytes in size, with
> a very low memory footprint.
>
>
> Future Enhancements
> -------------------
>
> All of this new functionality lays the groundwork for even more
> powerful enhancements down the road:
>
> - Top-to-bottom line sweep for Asian scripts
> - Bi-directional text (for Hebrew, Arabic, and others)
> - Bulleted and numbered text lists
> - HTML-inspired inline text tables
> - Inline attachments (for example, images that flow with text)
> - Advanced typographic features such as tracking, pairwise kerning,
> ligatures, etc.
> - Hyphenation support
> - Glyph substitution using fallback fonts
> - and more...
>
>
> Again, we're really excited to be sharing this code with the
> community. We'll be creating the proposals for the various components
> in the coming weeks and announcing them on the fw-formats list when
> they're ready for review. In the meantime, if you have any high-level
> questions, please don't hesitate to ask.
>
> --
>
> Willie Alberty, Owner
> Spenlen Media
> willie@spenlen.com
>
> http://www.spenlen.com/
>
>
>
--
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