Dégradé et fonction

<?php

declare(strict_types=1);

use PDF\Document\Fonts\StandardFont;
use PDF\Document\Fonts\Type1Font;
use PDF\Document\ResourceDictionary;
use PDF\Document\Resources\Font;
use PDF\Document\Resources\Shading;
use PDF\FileStructure;
use PDF\Functions\Domain;
use PDF\Functions\ExponentialInterpolationFunction;
use PDF\Functions\NumberArray;
use PDF\Functions\NumberInterval;
use PDF\Functions\Range;
use PDF\Specification\Dictionary\ShadingDictionaryTable78\ColorSpaceEntry;
use PDF\Specification\Dictionary\ShadingDictionaryTable78\ShadingTypeEntry;
use PDF\Specification\Dictionary\Type2ShadingDictionaryTable80;
use PDF\Specification\Dictionary\Type2ShadingDictionaryTable80\CoordsEntry;
use PDF\Specification\Dictionary\Type2ShadingDictionaryTable80\DomainEntry;
use PDF\Specification\Dictionary\Type2ShadingDictionaryTable80\ExtendEntry;
use PDF\Specification\Dictionary\Type2ShadingDictionaryTable80\FunctionEntry;
use PDF\Syntax\ContentStreamsResources\ContentStreams;
use PDF\Syntax\ContentStreamsResources\Operators\AppendRectangle;
use PDF\Syntax\ContentStreamsResources\Operators\BeginTextObject;
use PDF\Syntax\ContentStreamsResources\Operators\ClipPathNonzero;
use PDF\Syntax\ContentStreamsResources\Operators\EndPath;
use PDF\Syntax\ContentStreamsResources\Operators\EndTextObject;
use PDF\Syntax\ContentStreamsResources\Operators\MoveTextPosition;
use PDF\Syntax\ContentStreamsResources\Operators\PaintShading;
use PDF\Syntax\ContentStreamsResources\Operators\RestoreGraphicsState;
use PDF\Syntax\ContentStreamsResources\Operators\SaveGraphicsState;
use PDF\Syntax\ContentStreamsResources\Operators\SetNonstrokingRGBColor;
use PDF\Syntax\ContentStreamsResources\Operators\SetTextFontAndSize;
use PDF\Syntax\ContentStreamsResources\Operators\ShowText;
use PDF\Syntax\DataStructure\Rectangle;
use PDF\Syntax\DocumentStructure\DocumentCatalog;
use PDF\Syntax\DocumentStructure\PageTree\PageObject;
use PDF\Syntax\DocumentStructure\PageTree\PageTreeNode;
use PDF\Syntax\FileStructure\FileBody;
use PDF\Syntax\FileStructure\FileHeader;
use PDF\Syntax\Object\ArrayType;
use PDF\Syntax\Object\BooleanType;
use PDF\Syntax\Object\DictionaryObject\Entry;
use PDF\Syntax\Object\DictionaryType;
use PDF\Syntax\Object\IndirectReference;
use PDF\Syntax\Object\IntegerType;
use PDF\Syntax\Object\NameType;
use PDF\Syntax\Object\NumericType;
use PDF\Syntax\Object\StreamObject;
use PDF\Syntax\Object\StringObject\LiteralString;

require dirname(__DIR__) . '/vendor/autoload.php';

// 1. The type 2 PDF function receives a parameter t in [0, 1] and returns
//    three RGB components. With N=1, C(t)=C0+t*(C1-C0) is linear.
//    Range explicitly defines three output intervals, one per component.
$unitInterval = new NumberInterval(new NumericType(0), new NumericType(1));
$domain = new Domain($unitInterval);
$function = new ExponentialInterpolationFunction(
    $domain,
    new NumericType(1),
    new NumberArray(new NumericType(0.10), new NumericType(0.65), new NumericType(0.85)),
    new NumberArray(new NumericType(1.00), new NumericType(0.72), new NumericType(0.20)),
    new Range($unitInterval, $unitInterval, $unitInterval),
);

// 2. /ShadingType 2 is an axial gradient. /Coords describes its endpoints
//    in page coordinates: [64 500 548 500]. On the left t=0,
//    on the right t=1; color remains constant perpendicular to the axis.
//    Common entries come from Table 78, specific entries from Table 80.
//    The function remains an indirect object distinct from the shading dictionary.
$shading = new Type2ShadingDictionaryTable80(
    new ShadingTypeEntry(new IntegerType(2)),
    new ColorSpaceEntry(new NameType('DeviceRGB')),
    new CoordsEntry(new NumberArray(
        new NumericType(64),
        new NumericType(500),
        new NumericType(548),
        new NumericType(500),
    )),
    new DomainEntry($domain),
    new FunctionEntry(new IndirectReference($function)),
    new ExtendEntry(new ArrayType(new BooleanType(false), new BooleanType(false))),
);

// 3. /Shading associates local name /Sh1 with this dictionary. The sh operator
//    will invoke this resource; no bitmap or colored bands are created.
$helvetica = new Type1Font(StandardFont::Helvetica);
$resources = new ResourceDictionary(
    new Font(new DictionaryType(
        new Entry(new NameType('F1'), new IndirectReference($helvetica)),
    )),
    new Shading(new DictionaryType(
        new Entry(new NameType('Sh1'), new IndirectReference($shading)),
    )),
);

// 4. Shading fills its area within the current clipping path. re creates
//    a rectangle; W requests using it as the clipping area; n ends the
//    path without painting and applies clipping. q/Q limit its effect
//    to the gradient: subsequent text returns to the page clipping path.
$contents = new StreamObject(new ContentStreams(
    new SetNonstrokingRGBColor(new NumericType(0.08), new NumericType(0.18), new NumericType(0.28)),
    new BeginTextObject(),
    new SetTextFontAndSize(new NameType('F1'), new NumericType(26)),
    new MoveTextPosition(new NumericType(64), new NumericType(714)),
    new ShowText(new LiteralString('Un degrade calcule par le lecteur PDF')),
    new SetTextFontAndSize(new NameType('F1'), new NumericType(12)),
    new MoveTextPosition(new NumericType(0), new NumericType(-30)),
    new ShowText(new LiteralString('Fonction type 2 + shading axial type 2 + clipping rectangulaire')),
    new EndTextObject(),
    new SaveGraphicsState(),
    new AppendRectangle(new NumericType(64), new NumericType(400), new NumericType(484), new NumericType(200)),
    new ClipPathNonzero(),
    new EndPath(),
    new PaintShading(new NameType('Sh1')),
    new RestoreGraphicsState(),
    new BeginTextObject(),
    new SetTextFontAndSize(new NameType('F1'), new NumericType(14)),
    new MoveTextPosition(new NumericType(64), new NumericType(374)),
    new ShowText(new LiteralString('t = 0  |  C0 = [0.10 0.65 0.85]')),
    new MoveTextPosition(new NumericType(250), new NumericType(0)),
    new ShowText(new LiteralString('t = 1  |  C1 = [1.00 0.72 0.20]')),
    new SetTextFontAndSize(new NameType('F1'), new NumericType(12)),
    new MoveTextPosition(new NumericType(-250), new NumericType(-58)),
    new ShowText(new LiteralString('C(t) = C0 + t * (C1 - C0), car N = 1.')),
    new MoveTextPosition(new NumericType(0), new NumericType(-24)),
    new ShowText(new LiteralString('Coords fixe un axe ; le rectangle de clipping fixe la surface visible.')),
    new MoveTextPosition(new NumericType(0), new NumericType(-24)),
    new ShowText(new LiteralString('Ce texte reste visible hors du rectangle grace a la restauration Q.')),
    new EndTextObject(),
));

// 5. The same document graph as in other tutorials produces the file.
//    Indirect references are numbered during serialization.
$page = new PageObject(
    new Rectangle(new NumericType(0), new NumericType(0), new NumericType(612), new NumericType(792)),
    $resources,
    $contents,
);
$pages = (new PageTreeNode())->addKid($page);
$catalog = new DocumentCatalog($pages);
$file = new FileStructure(new FileHeader('1.7'), new FileBody($catalog), new IndirectReference($catalog));
$path = $argv[1] ?? __DIR__ . '/gradient.pdf';
$file->writeTo($path);
echo $path . PHP_EOL;