从 Node.js 中演示文稿形状提取图像

概述

演示文稿中的图像可以出现在多种形状类型中：普通图片框、作为形状填充的图片、OLE 对象预览图像、视频或音频帧的缩略图、缩放图像，或嵌套在表格、图表和 SmartArt 形状内部的图像。Aspose.Slides 将这些图像存储在演示文稿的图像集合中，可通过 ImageCollection 和 PPImage 对象访问。

如果您只需导出演示文稿中嵌入的每个图像资源，可遍历 presentation.getImages()。本文关注的是另一项任务：遍历形状以查找图像在幻灯片上的使用位置，从而保存的文件能够保留有用的上下文信息，例如幻灯片编号、形状位置和来源类型（图片框、填充图像、媒体预览、OLE 预览或缩放图像）。

Tip

使用 PPImage 及其 getBinaryData() 方法可保留原始编码的图像数据和文件类型。当您希望将输出统一为特定格式（例如 PNG）时，请使用 getImage()。

共享帮助方法

下面的帮助方法使示例保持简洁。saveOriginalImage 写入原始嵌入的字节，根据 MIME 类型选择安全的扩展名，并通过 SHA-256 哈希跳过重复的图像二进制数据。

const fileSystem = require("fs");
const pathModule = require("path");
const cryptoModule = require("crypto");
const asposeSlides = require("aspose.slides.via.java");

class ShapeReference {
    constructor(shape, namePart) {
        this.shape = shape;
        this.namePart = namePart;
    }
}

function saveOriginalImage(image, outputDirectory, fileNameBase, savedImageHashes) {
    const imageData = image.getBinaryData();
    const imageBuffer = Buffer.from(imageData);
    const imageHash = getSha256Hash(imageBuffer);
    if (savedImageHashes.has(imageHash)) {
        return false;
    }

    savedImageHashes.add(imageHash);

    const extension = getExtensionFromContentType(image.getContentType());
    const fileName = `${fileNameBase}.${extension}`;
    const outputPath = pathModule.join(outputDirectory, fileName);
    fileSystem.writeFileSync(outputPath, imageBuffer);
    return true;
}

function saveImageAsPng(image, outputDirectory, fileNameBase) {
    const fileName = `${fileNameBase}.png`;
    const outputPath = pathModule.join(outputDirectory, fileName);

    const outputImage = image.getImage();
    try {
        outputImage.save(outputPath, asposeSlides.ImageFormat.Png);
    } finally {
        if (outputImage !== null) {
            outputImage.dispose();
        }
    }
}

function getPictureFillImage(fillFormat) {
    if (fillFormat == null || fillFormat.getFillType() !== asposeSlides.FillType.Picture) {
        return null;
    }

    return fillFormat.getPictureFillFormat().getPicture().getImage();
}

function enumerateShapes(shapes, prefix, includeGroupedShapes) {
    const shapeReferences = [];
    const shapeCount = shapes.size();
    for (let shapeIndex = 0; shapeIndex < shapeCount; shapeIndex++) {
        const shape = shapes.get_Item(shapeIndex);
        const displayIndex = shapeIndex + 1;
        const shapeNamePart = `${prefix}_shape_${displayIndex}`;
        const shapeReference = new ShapeReference(shape, shapeNamePart);
        shapeReferences.push(shapeReference);

        if (includeGroupedShapes && java.instanceOf(shape, "com.aspose.slides.GroupShape")) {
            const childShapes = shape.getShapes();
            const childReferences = enumerateShapes(childShapes, shapeNamePart, includeGroupedShapes);
            shapeReferences.push(...childReferences);
        }
    }

    return shapeReferences;
}

function getSha256Hash(data) {
    return cryptoModule.createHash("sha256").update(data).digest("hex");
}

function getExtensionFromContentType(contentType) {
    if (contentType == null || contentType.trim().length === 0) {
        return "bin";
    }

    const mediaType = contentType.split(";")[0].trim().toLowerCase();
    if (mediaType === "image/jpeg") {
        return "jpg";
    }

    if (mediaType === "image/png") {
        return "png";
    }

    if (mediaType === "image/gif") {
        return "gif";
    }

    if (mediaType === "image/bmp") {
        return "bmp";
    }

    if (mediaType === "image/tiff") {
        return "tiff";
    }

    if (mediaType === "image/x-emf" || mediaType === "image/emf") {
        return "emf";
    }

    if (mediaType === "image/x-wmf" || mediaType === "image/wmf") {
        return "wmf";
    }

    if (mediaType === "image/svg+xml") {
        return "svg";
    }

    if (mediaType.startsWith("image/")) {
        const extension = mediaType.substring("image/".length);
        return makeSafeFileNamePart(extension);
    }

    return "bin";
}

function makeSafeFileNamePart(value) {
    return value.replace(/[^A-Za-z0-9._-]/g, "_");
}

从图片框提取图像

当图片作为独立对象插入时使用此方法。PictureFrame 将其图片存储在 getPictureFormat().getPicture().getImage() 中，该方法返回一个 PPImage 对象。

const inputPath = "sample.pptx";
const currentDirectory = process.cwd();
const outputDirectory = pathModule.join(currentDirectory, "extracted-images");
fileSystem.mkdirSync(outputDirectory, { recursive: true });

const savedImageHashes = new Set();

const presentation = new asposeSlides.Presentation(inputPath);
try {
    const slideCount = presentation.getSlides().size();
    for (let slideIndex = 0; slideIndex < slideCount; slideIndex++) {
        const slide = presentation.getSlides().get_Item(slideIndex);
        const slideNumber = slide.getSlideNumber();
        const slidePrefix = `slide_${slideNumber}`;
        const shapes = slide.getShapes();
        const shapeReferences = enumerateShapes(shapes, slidePrefix, false);
        for (const shapeReference of shapeReferences) {
            if (java.instanceOf(shapeReference.shape, "com.aspose.slides.PictureFrame")) {
                const pictureFrame = shapeReference.shape;
                const image = pictureFrame.getPictureFormat().getPicture().getImage();
                saveOriginalImage(image, outputDirectory, shapeReference.namePart, savedImageHashes);
            }
        }
    }
} finally {
    if (presentation !== null) {
        presentation.dispose();
    }
}

从填充图片的形状提取图像

形状可以使用图片作为填充。首先检查形状的填充类型：如果不是 FillType.Picture，则该填充不包含可提取的图片。下面的示例处理 AutoShape 对象，并通过 PPImage 的 getImage() 方法将每个图像保存为 PNG。

const inputPath = "sample.pptx";
const currentDirectory = process.cwd();
const outputDirectory = pathModule.join(currentDirectory, "shape-fill-images");
fileSystem.mkdirSync(outputDirectory, { recursive: true });

const presentation = new asposeSlides.Presentation(inputPath);
try {
    const slideCount = presentation.getSlides().size();
    for (let slideIndex = 0; slideIndex < slideCount; slideIndex++) {
        const slide = presentation.getSlides().get_Item(slideIndex);
        const slideNumber = slide.getSlideNumber();
        const slidePrefix = `slide_${slideNumber}`;
        const shapes = slide.getShapes();
        const shapeReferences = enumerateShapes(shapes, slidePrefix, false);
        for (const shapeReference of shapeReferences) {
            if (java.instanceOf(shapeReference.shape, "com.aspose.slides.AutoShape")) {
                const autoShape = shapeReference.shape;
                const fillFormat = autoShape.getFillFormat();
                const image = getPictureFillImage(fillFormat);
                if (image !== null) {
                    saveImageAsPng(image, outputDirectory, shapeReference.namePart);
                }
            }
        }
    }
} finally {
    if (presentation !== null) {
        presentation.dispose();
    }
}

从 OLE 对象框提取预览图像

OleObjectFrame 可以拥有 PowerPoint 用作对象在幻灯片上预览的替代图片。该图像可通过 getSubstitutePictureFormat().getPicture().getImage() 获得。提取此图片得到的是预览图像，而不是嵌入的 OLE 包内容。

const inputPath = "sample.pptx";
const currentDirectory = process.cwd();
const outputDirectory = pathModule.join(currentDirectory, "ole-preview-images");
fileSystem.mkdirSync(outputDirectory, { recursive: true });

const savedImageHashes = new Set();

const presentation = new asposeSlides.Presentation(inputPath);
try {
    const slideCount = presentation.getSlides().size();
    for (let slideIndex = 0; slideIndex < slideCount; slideIndex++) {
        const slide = presentation.getSlides().get_Item(slideIndex);
        const slideNumber = slide.getSlideNumber();
        const slidePrefix = `slide_${slideNumber}`;
        const shapes = slide.getShapes();
        const shapeReferences = enumerateShapes(shapes, slidePrefix, false);
        for (const shapeReference of shapeReferences) {
            if (java.instanceOf(shapeReference.shape, "com.aspose.slides.OleObjectFrame")) {
                const oleObjectFrame = shapeReference.shape;
                const image = oleObjectFrame.getSubstitutePictureFormat().getPicture().getImage();
                if (image !== null) {
                    const fileNameBase = `${shapeReference.namePart}_ole_preview`;
                    saveOriginalImage(image, outputDirectory, fileNameBase, savedImageHashes);
                }
            }
        }
    }
} finally {
    if (presentation !== null) {
        presentation.dispose();
    }
}

从视频帧提取预览图像

VideoFrame 也可以在 getPictureFormat().getPicture().getImage() 中存储预览图像。这是幻灯片上显示的海报或缩略图，而不是从视频流解码的帧。

const inputPath = "sample.pptx";
const currentDirectory = process.cwd();
const outputDirectory = pathModule.join(currentDirectory, "video-preview-images");
fileSystem.mkdirSync(outputDirectory, { recursive: true });

const savedImageHashes = new Set();

const presentation = new asposeSlides.Presentation(inputPath);
try {
    const slideCount = presentation.getSlides().size();
    for (let slideIndex = 0; slideIndex < slideCount; slideIndex++) {
        const slide = presentation.getSlides().get_Item(slideIndex);
        const slideNumber = slide.getSlideNumber();
        const slidePrefix = `slide_${slideNumber}`;
        const shapes = slide.getShapes();
        const shapeReferences = enumerateShapes(shapes, slidePrefix, false);
        for (const shapeReference of shapeReferences) {
            if (java.instanceOf(shapeReference.shape, "com.aspose.slides.VideoFrame")) {
                const videoFrame = shapeReference.shape;
                const image = videoFrame.getPictureFormat().getPicture().getImage();
                if (image !== null) {
                    const fileNameBase = `${shapeReference.namePart}_video_preview`;
                    saveOriginalImage(image, outputDirectory, fileNameBase, savedImageHashes);
                }
            }
        }
    }
} finally {
    if (presentation !== null) {
        presentation.dispose();
    }
}

从音频帧提取预览图像

AudioFrame 可以在 getPictureFormat().getPicture().getImage() 中存储缩略图。这是幻灯片上音频对象显示的图像。

const inputPath = "sample.pptx";
const currentDirectory = process.cwd();
const outputDirectory = pathModule.join(currentDirectory, "audio-preview-images");
fileSystem.mkdirSync(outputDirectory, { recursive: true });

const savedImageHashes = new Set();

const presentation = new asposeSlides.Presentation(inputPath);
try {
    const slideCount = presentation.getSlides().size();
    for (let slideIndex = 0; slideIndex < slideCount; slideIndex++) {
        const slide = presentation.getSlides().get_Item(slideIndex);
        const slideNumber = slide.getSlideNumber();
        const slidePrefix = `slide_${slideNumber}`;
        const shapes = slide.getShapes();
        const shapeReferences = enumerateShapes(shapes, slidePrefix, false);
        for (const shapeReference of shapeReferences) {
            if (java.instanceOf(shapeReference.shape, "com.aspose.slides.AudioFrame")) {
                const audioFrame = shapeReference.shape;
                const image = audioFrame.getPictureFormat().getPicture().getImage();
                if (image !== null) {
                    const fileNameBase = `${shapeReference.namePart}_audio_preview`;
                    saveOriginalImage(image, outputDirectory, fileNameBase, savedImageHashes);
                }
            }
        }
    }
} finally {
    if (presentation !== null) {
        presentation.dispose();
    }
}

从缩放对象提取图像

ZoomFrame 和 SectionZoomFrame 形状可以使用自定义图像。请从缩放框读取 getZoomImage()。

const inputPath = "sample.pptx";
const currentDirectory = process.cwd();
const outputDirectory = pathModule.join(currentDirectory, "zoom-images");
fileSystem.mkdirSync(outputDirectory, { recursive: true });

const savedImageHashes = new Set();

const presentation = new asposeSlides.Presentation(inputPath);
try {
    const slideCount = presentation.getSlides().size();
    for (let slideIndex = 0; slideIndex < slideCount; slideIndex++) {
        const slide = presentation.getSlides().get_Item(slideIndex);
        const slideNumber = slide.getSlideNumber();
        const slidePrefix = `slide_${slideNumber}`;
        const shapes = slide.getShapes();
        const shapeReferences = enumerateShapes(shapes, slidePrefix, false);
        for (const shapeReference of shapeReferences) {
            if (java.instanceOf(shapeReference.shape, "com.aspose.slides.ZoomFrame")) {
                const zoomFrame = shapeReference.shape;
                const image = zoomFrame.getZoomImage();
                if (image !== null) {
                    const fileNameBase = `${shapeReference.namePart}_zoom`;
                    saveOriginalImage(image, outputDirectory, fileNameBase, savedImageHashes);
                    continue;
                }
            }

            if (java.instanceOf(shapeReference.shape, "com.aspose.slides.SectionZoomFrame")) {
                const sectionZoomFrame = shapeReference.shape;
                const image = sectionZoomFrame.getZoomImage();
                if (image !== null) {
                    const fileNameBase = `${shapeReference.namePart}_section_zoom`;
                    saveOriginalImage(image, outputDirectory, fileNameBase, savedImageHashes);
                    continue;
                }
            }
        }
    }
} finally {
    if (presentation !== null) {
        presentation.dispose();
    }
}

从概览缩放框提取图像

SummaryZoomFrame 也是一种形状。其各节项可以使用自定义图像，通过每个概览缩放节的 getZoomImage() 方法获取。

const inputPath = "sample.pptx";
const currentDirectory = process.cwd();
const outputDirectory = pathModule.join(currentDirectory, "summary-zoom-images");
fileSystem.mkdirSync(outputDirectory, { recursive: true });

const savedImageHashes = new Set();

const presentation = new asposeSlides.Presentation(inputPath);
try {
    const slideCount = presentation.getSlides().size();
    for (let slideIndex = 0; slideIndex < slideCount; slideIndex++) {
        const slide = presentation.getSlides().get_Item(slideIndex);
        const slideNumber = slide.getSlideNumber();
        const slidePrefix = `slide_${slideNumber}`;
        const shapes = slide.getShapes();
        const shapeReferences = enumerateShapes(shapes, slidePrefix, false);
        for (const shapeReference of shapeReferences) {
            if (java.instanceOf(shapeReference.shape, "com.aspose.slides.SummaryZoomFrame")) {
                const summaryZoomFrame = shapeReference.shape;
                const summaryZoomCollection = summaryZoomFrame.getSummaryZoomCollection();
                const sectionCount = summaryZoomCollection.size();
                for (let sectionIndex = 0; sectionIndex < sectionCount; sectionIndex++) {
                    const summaryZoomSection = summaryZoomCollection.get_Item(sectionIndex);
                    const image = summaryZoomSection.getZoomImage();
                    if (image !== null) {
                        const displayIndex = sectionIndex + 1;
                        const fileNameBase = `${shapeReference.namePart}_summary_zoom_${displayIndex}`;
                        saveOriginalImage(image, outputDirectory, fileNameBase, savedImageHashes);
                    }
                }
            }
        }
    }
} finally {
    if (presentation !== null) {
        presentation.dispose();
    }
}

从表格形状提取图像

Table 是一种形状。表格中的图像通常存储为单元格的图片填充。

const inputPath = "sample.pptx";
const currentDirectory = process.cwd();
const outputDirectory = pathModule.join(currentDirectory, "table-images");
fileSystem.mkdirSync(outputDirectory, { recursive: true });

const savedImageHashes = new Set();

const presentation = new asposeSlides.Presentation(inputPath);
try {
    const slideCount = presentation.getSlides().size();
    for (let slideIndex = 0; slideIndex < slideCount; slideIndex++) {
        const slide = presentation.getSlides().get_Item(slideIndex);
        const slideNumber = slide.getSlideNumber();
        const slidePrefix = `slide_${slideNumber}`;
        const shapes = slide.getShapes();
        const shapeReferences = enumerateShapes(shapes, slidePrefix, true);
        for (const shapeReference of shapeReferences) {
            if (java.instanceOf(shapeReference.shape, "com.aspose.slides.Table")) {
                const table = shapeReference.shape;
                const rowCount = table.getRows().size();
                const columnCount = table.getColumns().size();
                for (let rowIndex = 0; rowIndex < rowCount; rowIndex++) {
                    for (let columnIndex = 0; columnIndex < columnCount; columnIndex++) {
                        const cell = table.get_Item(columnIndex, rowIndex);
                        const fillFormat = cell.getCellFormat().getFillFormat();
                        const image = getPictureFillImage(fillFormat);
                        if (image !== null) {
                            const displayRow = rowIndex + 1;
                            const displayColumn = columnIndex + 1;
                            const fileNameBase = `${shapeReference.namePart}_cell_${displayRow}_${displayColumn}`;
                            saveOriginalImage(image, outputDirectory, fileNameBase, savedImageHashes);
                        }
                    }
                }
            }
        }
    }
} finally {
    if (presentation !== null) {
        presentation.dispose();
    }
}

从图表形状提取图像

Chart 是一种形状。下面的示例从图表区域的图片填充中提取图像。

const inputPath = "sample.pptx";
const currentDirectory = process.cwd();
const outputDirectory = pathModule.join(currentDirectory, "chart-images");
fileSystem.mkdirSync(outputDirectory, { recursive: true });

const savedImageHashes = new Set();

const presentation = new asposeSlides.Presentation(inputPath);
try {
    const slideCount = presentation.getSlides().size();
    for (let slideIndex = 0; slideIndex < slideCount; slideIndex++) {
        const slide = presentation.getSlides().get_Item(slideIndex);
        const slideNumber = slide.getSlideNumber();
        const slidePrefix = `slide_${slideNumber}`;
        const shapes = slide.getShapes();
        const shapeReferences = enumerateShapes(shapes, slidePrefix, true);
        for (const shapeReference of shapeReferences) {
            if (java.instanceOf(shapeReference.shape, "com.aspose.slides.Chart")) {
                const chart = shapeReference.shape;
                const fillFormat = chart.getFillFormat();
                const image = getPictureFillImage(fillFormat);
                if (image !== null) {
                    const fileNameBase = `${shapeReference.namePart}_chart_area`;
                    saveOriginalImage(image, outputDirectory, fileNameBase, savedImageHashes);
                }
            }
        }
    }
} finally {
    if (presentation !== null) {
        presentation.dispose();
    }
}

从 SmartArt 形状提取图像

SmartArt 对象是一种形状。根据 SmartArt 布局，图像可能存储在节点项目符号填充中或节点形状的填充格式中。

const inputPath = "sample.pptx";
const currentDirectory = process.cwd();
const outputDirectory = pathModule.join(currentDirectory, "smartart-images");
fileSystem.mkdirSync(outputDirectory, { recursive: true });

const savedImageHashes = new Set();

const presentation = new asposeSlides.Presentation(inputPath);
try {
    const slideCount = presentation.getSlides().size();
    for (let slideIndex = 0; slideIndex < slideCount; slideIndex++) {
        const slide = presentation.getSlides().get_Item(slideIndex);
        const slideNumber = slide.getSlideNumber();
        const slidePrefix = `slide_${slideNumber}`;
        const shapes = slide.getShapes();
        const shapeReferences = enumerateShapes(shapes, slidePrefix, true);
        for (const shapeReference of shapeReferences) {
            if (java.instanceOf(shapeReference.shape, "com.aspose.slides.SmartArt")) {
                const smartArt = shapeReference.shape;
                const allNodes = smartArt.getAllNodes();
                const nodeCount = allNodes.size();
                for (let nodeIndex = 0; nodeIndex < nodeCount; nodeIndex++) {
                    const node = allNodes.get_Item(nodeIndex);
                    const bulletFillFormat = node.getBulletFillFormat();
                    const bulletImage = getPictureFillImage(bulletFillFormat);
                    if (bulletImage !== null) {
                        const displayNode = nodeIndex + 1;
                        const fileNameBase = `${shapeReference.namePart}_smartart_node_${displayNode}_bullet`;
                        saveOriginalImage(bulletImage, outputDirectory, fileNameBase, savedImageHashes);
                    }

                    const nodeShapes = node.getShapes();
                    const nodeShapeCount = nodeShapes.size();
                    for (let nodeShapeIndex = 0; nodeShapeIndex < nodeShapeCount; nodeShapeIndex++) {
                        const nodeShape = nodeShapes.get_Item(nodeShapeIndex);
                        const fillFormat = nodeShape.getFillFormat();
                        const image = getPictureFillImage(fillFormat);
                        if (image !== null) {
                            const displayNode = nodeIndex + 1;
                            const displayNodeShape = nodeShapeIndex + 1;
                            const fileNameBase = `${shapeReference.namePart}_smartart_node_${displayNode}_shape_${displayNodeShape}`;
                            saveOriginalImage(image, outputDirectory, fileNameBase, savedImageHashes);
                        }
                    }
                }
            }
        }
    }
} finally {
    if (presentation !== null) {
        presentation.dispose();
    }
}

在组合形状中包含图像

组合形状包含其自己的形状集合。共享的 enumerateShapes 帮助方法具有 includeGroupedShapes 选项。当您想检查 GroupShape 对象内部的形状时，将其设为 true。下面的示例提取图片框、填充图片的形状、OLE 对象预览、视频帧缩略图和音频帧缩略图中的图像。要同时包含表格、图表、SmartArt 和概览缩放图像，请复用前述章节的专用提取逻辑，并保持相同的递归形状遍历。

const inputPath = "sample.pptx";
const currentDirectory = process.cwd();
const outputDirectory = pathModule.join(currentDirectory, "all-shape-images");
fileSystem.mkdirSync(outputDirectory, { recursive: true });

const savedImageHashes = new Set();

const presentation = new asposeSlides.Presentation(inputPath);
try {
    const slideCount = presentation.getSlides().size();
    for (let slideIndex = 0; slideIndex < slideCount; slideIndex++) {
        const slide = presentation.getSlides().get_Item(slideIndex);
        const slideNumber = slide.getSlideNumber();
        const slidePrefix = `slide_${slideNumber}`;
        const shapes = slide.getShapes();
        const shapeReferences = enumerateShapes(shapes, slidePrefix, true);
        for (const shapeReference of shapeReferences) {
            if (java.instanceOf(shapeReference.shape, "com.aspose.slides.OleObjectFrame")) {
                const oleObjectFrame = shapeReference.shape;
                const image = oleObjectFrame.getSubstitutePictureFormat().getPicture().getImage();
                if (image !== null) {
                    const fileNameBase = `${shapeReference.namePart}_ole_preview`;
                    saveOriginalImage(image, outputDirectory, fileNameBase, savedImageHashes);
                }

                continue;
            }

            if (java.instanceOf(shapeReference.shape, "com.aspose.slides.VideoFrame")) {
                const videoFrame = shapeReference.shape;
                const image = videoFrame.getPictureFormat().getPicture().getImage();
                if (image !== null) {
                    const fileNameBase = `${shapeReference.namePart}_video_preview`;
                    saveOriginalImage(image, outputDirectory, fileNameBase, savedImageHashes);
                }

                continue;
            }

            if (java.instanceOf(shapeReference.shape, "com.aspose.slides.AudioFrame")) {
                const audioFrame = shapeReference.shape;
                const image = audioFrame.getPictureFormat().getPicture().getImage();
                if (image !== null) {
                    const fileNameBase = `${shapeReference.namePart}_audio_preview`;
                    saveOriginalImage(image, outputDirectory, fileNameBase, savedImageHashes);
                }

                continue;
            }

            if (java.instanceOf(shapeReference.shape, "com.aspose.slides.PictureFrame")) {
                const pictureFrame = shapeReference.shape;
                const image = pictureFrame.getPictureFormat().getPicture().getImage();
                saveOriginalImage(image, outputDirectory, shapeReference.namePart, savedImageHashes);
                continue;
            }

            if (java.instanceOf(shapeReference.shape, "com.aspose.slides.AutoShape")) {
                const autoShape = shapeReference.shape;
                const fillFormat = autoShape.getFillFormat();
                const image = getPictureFillImage(fillFormat);
                if (image !== null) {
                    saveOriginalImage(image, outputDirectory, shapeReference.namePart, savedImageHashes);
                }
            }
        }
    }
} finally {
    if (presentation !== null) {
        presentation.dispose();
    }
}

边缘情况和实用说明

• 重复图像： 多个形状可能引用相同的图像，或是字节相同的不同图像。在写入文件之前，对 getBinaryData() 返回的 PPImage 数据进行哈希，以实现每个唯一图像仅输出一个文件。
• 原始数据 与 转换后输出： 从 getBinaryData() 中保存 PPImage 数据可保留嵌入的 JPEG、PNG、GIF、SVG、EMF 或 WMF 数据。当您希望统一输出格式时，保存 getImage() 返回的图像会更有用。
• 不支持的填充类型： 实心、渐变、图案和无填充的形状不包含图片填充。在读取 getPictureFillFormat() 之前，请检查 FillType。
• 组合形状： 顶层幻灯片形状集合不会展开组合。若组合内容重要，请通过 getShapes() 递归检查 GroupShape 的内容。
• OLE 对象预览： OleObjectFrame 可能通过 getSubstitutePictureFormat() 提供预览图像，但该图像仅是幻灯片预览，而不是 OLE 对象内部的嵌入文件。
• 视频帧缩略图： VideoFrame 可能通过 getPictureFormat() 提供预览图像，但该图像仅是幻灯片上显示的海报，而不是从视频流中提取的。
• 音频帧缩略图： AudioFrame 可能通过 getPictureFormat() 提供图标或缩略图；这并非嵌入的音频数据。
• 缩放图像： 幻灯片缩放、节缩放和概览缩放形状可能通过 getZoomImage() 使用自定义的 PPImage 对象。
• 嵌套形状模型： 表格、图表和 SmartArt 对象实现了 Shape，但它们的图像通常存储在嵌套的表格单元格、图表元素或 SmartArt 节点的格式对象中。
• 裁剪或变换的图片： 访问 PPImage 可获得存储的图像资源。它不会呈现形状所施加的裁剪、透明度、重新着色、旋转或其他视觉效果。

常见问题

我可以提取原始图像而不进行裁剪、特效或形状转换吗？

可以。访问 PPImage 对象并将 getBinaryData() 的数据写入磁盘。这会保留演示文稿中存储的原始编码图像，而不是图像在幻灯片上的渲染方式。

我可以将所有提取的图像导出为 PNG 吗？

可以。使用 PPImage 及其 getImage() 方法，然后使用 ImageFormat 调用 save()。这会转换输出，可能无法保留原始文件类型或矢量数据。

如何避免多次保存相同的图像？

对 getBinaryData() 返回的 PPImage 数据计算哈希并将哈希存入集合。若新图像的哈希已存在，则跳过或记录对已有输出文件的另一次引用。

为什么某些形状未生成图像？

图片框、填充图片的形状、OLE 对象框、媒体框、缩放框、表格、图表和 SmartArt 对象都可能引用图像。某些形状类型通过嵌套的格式对象公开图像，因此仅检查 getPictureFormat() 或形状的 getFillFormat() 并不总是足够。

我可以提取视频帧显示的缩略图吗？

可以。使用 VideoFrame 并读取 getPictureFormat().getPicture().getImage()。这会提取随视频帧存储的海报图像，而不是从视频文件生成的帧。

如何确定演示文稿图像集合中的特定图像被哪些形状使用？

Aspose.Slides 不会存储从 PPImage 到形状的反向链接。遍历时构建映射：每当发现图像引用时，记录幻灯片编号、形状路径以及图像哈希或集合项。

我可以提取嵌入在 OLE 对象内部的图像，例如附件文档吗？

您可以从 OleObjectFrame 提取 OLE 对象的幻灯片预览。但该预览并不是嵌入的文档本身。若要提取嵌入文件内部的图像，需要先提取 OLE 数据，再使用相应文件类型的工具进行检查。