操作JPEG图像

使用ExifData类读取和修改JPEG EXIF标签

几乎所有数码相机（包括智能手机）、扫描仪和其他处理图像的系统都会保存带有EXIF（可交换图像文件）信息的图像。相机设置和场景信息被相机记录到图像文件中。EXIF数据还包括快门速度、拍摄日期和时间、焦距、曝光补偿、测光模式以及是否使用了闪光灯等信息。Aspose.Imaging APIs使得从给定图像中提取EXIF信息变得非常简单和方便。开发人员也可以根据自己的需求向图像中写入EXIF数据或修改现有信息。Aspose.Imaging已经为读取、写入和修改EXIF数据提供了ExifData类，而Aspose.PSD.Exif.Enums命名空间包含了该过程中使用的相关枚举。

读取EXIF数据

Aspose.PSD APIs提供了一种读取给定图像中EXIF数据的方法。下面提供的步骤演示了使用ExifData类读取图像中的EXIF信息。

• 使用工厂方法Load加载PSD图像。
• 在PSD资源中查找JPEG缩略图。
• 提取ExifData类的一个实例。

获取所需信息并将其写入控制台。

        String dataDir = Utils.getDataDir(ReadAllEXIFTags.class) + "ModifyingAndConvertingImages/";

        try (PsdImage image = (PsdImage) Image.load(dataDir + "1280px-Zebras_Serengeti.psd")) {
            // Iterate over resources.
            for (int i = 0; i < image.getImageResources().length; i++) {
                // Find thumbnail resource. Typically they are in the Jpeg file format.
                if (image.getImageResources()[i] instanceof ThumbnailResource || image.getImageResources()[i] instanceof Thumbnail4Resource) {
                    // Extract exif data and print to the console.
                    ThumbnailResource thumbnail = (ThumbnailResource) image.getImageResources()[i];
                    JpegExifData exif = thumbnail.getJpegOptions().getExifData();
                    if (exif != null) {

                        for (int j = 0; j < exif.getProperties().length; j++) {

                            System.out.println(exif.getProperties()[j].getId() + ":" + exif.getProperties()[j].getValue());
                        }

                    }
                }
            }
        }

开发人员还可以使用以下代码段获取特定信息。

        String dataDir = Utils.getDataDir(ReadSpecificEXIFTagsInformation.class) + "ModifyingAndConvertingImages/";

        try (PsdImage image = (PsdImage) Image.load(dataDir + "1280px-Zebras_Serengeti.psd")) {
// Iterate over resources.
            for (int i = 0; i < image.getImageResources().length; i++) {
                // Find thumbnail resource. Typically they are in the Jpeg file format.
                if (image.getImageResources()[i] instanceof ThumbnailResource || image.getImageResources()[i] instanceof Thumbnail4Resource) {
                    // Extract exif data and print to the console.
                    JpegExifData exif = ((ThumbnailResource) image.getImageResources()[i]).getJpegOptions().getExifData();
                    if (exif != null) {
                        System.out.println("Exif WhiteBalance: " + exif.getWhiteBalance());
                        System.out.println("Exif PixelXDimension: " + exif.getPixelXDimension());
                        System.out.println("Exif PixelYDimension: " + exif.getPixelYDimension());
                        System.out.println("Exif ISOSpeed: " + exif.getISOSpeed());
                        System.out.println("Exif FocalLength: " + exif.getFocalLength());
                    }
                }
            }
        }

写入和修改EXIF数据

使用Aspose.PSD APIs，开发人员可以写入新的EXIF信息并修改图像的现有EXIF数据。这两个过程（写入和修改）都需要加载图像并将EXIF数据获取到ExifData类的实例中。然后，可以访问ExifData类公开的属性并相应设置它们。请注意，用于操作的图像应为通常为PSD缩略图的JPEG或TIFF图像。演示如何使用的示例代码如下：

        String dataDir = Utils.getDataDir(WritingAndModifyingEXIFData.class) + "ModifyingAndConvertingImages/";

        try (PsdImage image = (PsdImage) Image.load(dataDir + "1280px-Zebras_Serengeti.psd")) {

// Iterate over resources.
            for (int i = 0; i < image.getImageResources().length; i++) {
                // Find thumbnail resource. Typically they are in the Jpeg file format.
                if (image.getImageResources()[i] instanceof ThumbnailResource || image.getImageResources()[i] instanceof Thumbnail4Resource) {
                    // Extract exif data and print to the console.
                    JpegExifData exif = ((ThumbnailResource) image.getImageResources()[i]).getJpegOptions().getExifData();
                    if (exif != null) {
                        // Set LensMake, WhiteBalance, Flash information Save the image
                        exif.setLensMake("Sony");
                        exif.setWhiteBalance(ExifWhiteBalance.Auto);
                        exif.setFlash(ExifFlash.Fired);

                    }
                }
            }
            image.save(dataDir + "aspose_out.psd");
        }

从PSD资源中提取缩略图

缩略图是图片的缩小版本，用于显示图片的一个重要部分而不是整个画面。一些图像文件（尤其是用数字相机拍摄的图像）中嵌入了一个缩略图像。Aspose.PSD API允许您提取PSD资源缩略图并将其单独存储在磁盘上。缩略资源包含ExifData.Thumbnail属性，可检索缩略图数据。下面提供的代码片段演示了如何使用它。

        String dataDir = Utils.getDataDir(ExtractThumbnailFromPSD.class) + "ModifyingAndConvertingImages/";

        try (PsdImage image = (PsdImage) Image.load(dataDir + "1280px-Zebras_Serengeti.psd")) {
// Iterate over resources.
            for (int i = 0; i < image.getImageResources().length; i++) {
                // Find thumbnail resource. Typically they are in the Jpeg file format.
                if (image.getImageResources()[i] instanceof ThumbnailResource || image.getImageResources()[i] instanceof Thumbnail4Resource) {
                    // Extract thumbnail data and store it as a separate image file.
                    ThumbnailResource thumbnail = (ThumbnailResource) image.getImageResources()[i];
                    int[] data = ((ThumbnailResource) image.getImageResources()[i]).getThumbnailArgb32Data();

                    try (PsdImage extractedThumnailImage = new PsdImage(thumbnail.getWidth(), thumbnail.getHeight())) {
                        extractedThumnailImage.saveArgb32Pixels(extractedThumnailImage.getBounds(), data);
                        extractedThumnailImage.save(dataDir + "extracted_thumbnail.jpg", new JpegOptions());
                    }
                }
            }
        }

使用上述讨论的方法将缩略图存储为其他支持的文件格式。如果您希望将缩略图数据导出为其他图像格式，如BMP和PNG，请使用其他图像导出选项。

从JFIF段提取缩略图

也可以从PSD缩略图资源的ExifData或JFIF段中提取缩略图。以下代码显示了如何从JFIF或ExifData段中提取缩略图数据：

        String dataDir = Utils.getDataDir(ExtractThumbnailFromPSD.class) + "ModifyingAndConvertingImages/";

        try (PsdImage image = (PsdImage) Image.load(dataDir + "1280px-Zebras_Serengeti.psd")) {
// Iterate over resources.
            for (int i = 0; i < image.getImageResources().length; i++) {
                // Find thumbnail resource. Typically they are in the Jpeg file format.
                if (image.getImageResources()[i] instanceof ThumbnailResource || image.getImageResources()[i] instanceof Thumbnail4Resource) {
                    // Extract thumbnail data and store it as a separate image file.
                    ThumbnailResource thumbnail = (ThumbnailResource) image.getImageResources()[i];
                    int[] data = ((ThumbnailResource) image.getImageResources()[i]).getThumbnailArgb32Data();

                    try (PsdImage extractedThumnailImage = new PsdImage(thumbnail.getWidth(), thumbnail.getHeight())) {
                        extractedThumnailImage.saveArgb32Pixels(extractedThumnailImage.getBounds(), data);
                        extractedThumnailImage.save(dataDir + "extracted_thumbnail.jpg", new JpegOptions());
                    }
                }
            }
        }

使用上述讨论的方法将缩略图存储为其他支持的文件格式。如果您希望将缩略图数据导出为其他图像格式，如BMP和PNG，请使用其他图像导出选项。

向JFIF段添加缩略图

下面的代码片段演示了如何使用JFIF.Thumbnail属性将缩略图图像添加到已加载的PSD图像的JFIF段中：

        String dataDir = Utils.getDataDir(AddThumbnailToJFIFSegment.class) + "ModifyingAndConvertingImages/";

        try (PsdImage image = (PsdImage) Image.load(dataDir + "1280px-Zebras_Serengeti.psd")) {
// Iterate over resources.
            for (int i = 0; i < image.getImageResources().length; i++) {
                // Find thumbnail resource. Typically they are in the Jpeg file format.
                if (image.getImageResources()[i] instanceof ThumbnailResource || image.getImageResources()[i] instanceof Thumbnail4Resource) {
                    // Adjust thumbnail data.
                    ThumbnailResource thumbnail = (ThumbnailResource) image.getImageResources()[i];
                    JpegExifData exifData = new JpegExifData();
                    PsdImage thumbnailImage = new PsdImage(100, 100);
                    try {
                        // Fill thumbnail data.
                        int[] pixels = new int[thumbnailImage.getWidth() * thumbnailImage.getHeight()];
                        for (int j = 0; j < pixels.length; j++) {
                            pixels[j] = j;
                        }

                        // Assign thumbnail data.
                        thumbnailImage.saveArgb32Pixels(thumbnailImage.getBounds(), pixels);
                        exifData.setThumbnail(thumbnailImage);
                        thumbnail.getJpegOptions().setExifData(exifData);
                    } catch (Exception e) {
                        thumbnailImage.dispose();

                    }
                }
            }

            image.save();
        }

由于JPEG格式规范限制，带有其他段数据的缩略图图像不能超过65545字节。如果要设置大图像作为缩略图，可能会引发异常。

向EXIF段添加缩略图

下面的代码片段演示了如何使用ExifData.Thumbnail属性将缩略图图像添加到已加载的PSD图像的EXIF段中：

        String dataDir = Utils.getDataDir(AddThumbnailToEXIFSegment.class) + "ModifyingAndConvertingImages/";

        try (PsdImage image = (PsdImage) Image.load(dataDir + "1280px-Zebras_Serengeti.psd")) {
// Iterate over resources.
            for (int i = 0; i < image.getImageResources().length; i++) {
                // Find thumbnail resource. Typically they are in the Jpeg file format.
                if (image.getImageResources()[i] instanceof ThumbnailResource || image.getImageResources()[i] instanceof Thumbnail4Resource) {
                    // Adjust thumbnail data.
                    ThumbnailResource thumbnail = (ThumbnailResource) image.getImageResources()[i];
                    JpegExifData exifData = new JpegExifData();
                    PsdImage thumbnailImage = new PsdImage(100, 100);
                    try {
                        // Fill thumbnail data.
                        int[] pixels = new int[thumbnailImage.getWidth() * thumbnailImage.getHeight()];
                        for (int j = 0; j < pixels.length; j++) {
                            pixels[j] = j;
                        }

                        // Assign thumbnail data.
                        thumbnailImage.saveArgb32Pixels(thumbnailImage.getBounds(), pixels);
                        exifData.setThumbnail(thumbnailImage);
                        thumbnail.getJpegOptions().setExifData(exifData);
                    } catch (Exception e) {
                        thumbnailImage.dispose();

                    }
                }
            }
            image.save();
        }

在这种情况下，Aspose.PSD API无法估算缩略图图像的大小，但可以检查整个EXIF数据段的大小。这个大小不能超过65535字节。

使用JpegExifData类读取和修改JPEG EXIF标签

Aspose.PSD APIs提供了JpegExifData类，专门用于JPEG图像格式以检索和更新EXIF信息。本文演示了使用JpegExifData类实现相同目的的方法。Aspose.PSD.Exif.JpegExifData类用于JPEG图像的EXIF数据容器，并提供获取标准JPEG EXIF标签的方法，如下所示：

        String dataDir = Utils.getDataDir(AddThumbnailToEXIFSegment.class) + "ModifyingAndConvertingImages/";

        try (PsdImage image = (PsdImage) Image.load(dataDir + "1280px-Zebras_Serengeti.psd")) {
// Iterate over resources.
            for (int i = 0; i < image.getImageResources().length; i++) {
                // Find thumbnail resource. Typically they are in the Jpeg file format.
                if (image.getImageResources()[i] instanceof ThumbnailResource || image.getImageResources()[i] instanceof Thumbnail4Resource) {
                    // Adjust thumbnail data.
                    ThumbnailResource thumbnail = (ThumbnailResource) image.getImageResources()[i];
                    JpegExifData exifData = new JpegExifData();
                    PsdImage thumbnailImage = new PsdImage(100, 100);
                    try {
                        // Fill thumbnail data.
                        int[] pixels = new int[thumbnailImage.getWidth() * thumbnailImage.getHeight()];
                        for (int j = 0; j < pixels.length; j++) {
                            pixels[j] = j;
                        }

                        // Assign thumbnail data.
                        thumbnailImage.saveArgb32Pixels(thumbnailImage.getBounds(), pixels);
                        exifData.setThumbnail(thumbnailImage);
                        thumbnail.getJpegOptions().setExifData(exifData);
                    } catch (Exception e) {
                        thumbnailImage.dispose();

                    }
                }
            }
            image.save();
        }

完整的EXIF标签列表

上面的代码段使用Aspose.PSD.Exif.JpegExifData类提供的属性读取了一些EXIF标签。这些属性的完整列表在这里。以下代码将使用System.Reflection.PropertyInfo类读取所有EXIF标签。

        String dataDir = Utils.getDataDir(ReadAllEXIFTagList.class) + "ModifyingAndConvertingImages/";

        try (PsdImage image = (PsdImage) Image.load(dataDir + "1280px-Zebras_Serengeti.psd")) {
// Iterate over resources.
            for (int i = 0; i < image.getImageResources().length; i++) {
                // Find thumbnail resource. Typically they are in the Jpeg file format.
                if (image.getImageResources()[i] instanceof ThumbnailResource || image.getImageResources()[i] instanceof Thumbnail4Resource) {
                    // Extract thumbnail data and store it as a separate image file.
                    ThumbnailResource thumbnail = (ThumbnailResource) image.getImageResources()[i];
                    JpegExifData exifData = thumbnail.getJpegOptions().getExifData();
                    if (exifData != null) {
                        for (int j = 0; j < exifData.getProperties().length; j++) {
                            System.out.println(exifData.getProperties()[j].getId() + ":" + exifData.getProperties()[j].getValue());
                        }

                    }
                }
            }
        }

自动校正JPEG图像的方向

拍摄的照片在相机旋转了90°、180°、270°或无（正常方向）时。大多数数码相机将方向信息与JPEG图像的EXIF标签一起存储。可以使用这些信息对图像执行自动旋转以纠正方向。Aspose.PSD APIs为JpegImage类提供了AutoRotate方法，用于自动校正JPEG图像的方向。以下是如何在Java API的Aspose.PSD中使用AutoRotate方法的示例。

        String dataDir = Utils.getDataDir(AutoCorrectOrientationOfJPEGImages.class) + "ModifyingAndConvertingImages/";

        try (PsdImage image = (PsdImage) Image.load(dataDir + "1280px-Zebras_Serengeti.psd")) {
            // Iterate over resources.
            for (int i = 0; i < image.getImageResources().length; i++) {
                // Find thumbnail resource. Typically they are in the Jpeg file format.
                if (image.getImageResources()[i] instanceof ThumbnailResource || image.getImageResources()[i] instanceof Thumbnail4Resource) {
                    // Adjust thumbnail data.
                    ThumbnailResource thumbnail = (ThumbnailResource) image.getImageResources()[i];
                    JpegExifData exifData = thumbnail.getJpegOptions().getExifData();
                    if (exifData != null && exifData.getThumbnail() != null) {
                        // If there is thumbnail stored then auto-rotate it.
                        JpegImage jpegImage = (JpegImage) exifData.getThumbnail();
                        if (jpegImage != null) {
                            jpegImage.autoRotate();
                        }
                    }
                }
            }
            // Save image.
            image.save();
        }

支持JPEG-LS与CMYK和YCCK

Aspose.PSD for Java API支持JPEG-LS中的CMYK和YCCK颜色模型。下面的代码片段演示了如何在JPEG-LS中使用该支持。

        String dataDir = Utils.getDataDir(SupportForJPEGLSWithCMYK.class) + "ModifyingAndConvertingImages/";

        try (PsdImage image = (PsdImage) Image.load(dataDir + "PsdImage.psd")) {

            JpegOptions options = new JpegOptions();
            //Just replace one line given below in examples to use YCCK instead of CMYK
            //options.ColorType = JpegCompressionColorMode.Cmyk;
            options.setColorType(JpegCompressionColorMode.Cmyk);
            options.setCompressionType(JpegCompressionMode.JpegLs);

            // The default profiles will be used.
            options.setRgbColorProfile(null);
            options.setCmykColorProfile(null);

            image.save(dataDir + "output.jpg", options);
        }

        try (PsdImage image1 = (PsdImage) Image.load(dataDir + "PsdImage.psd")) {
            JpegOptions options1 = new JpegOptions();
            //Just replace one line given below in examples to use YCCK instead of CMYK
            //options.ColorType = JpegCompressionColorMode.Cmyk;
            options1.setColorType(JpegCompressionColorMode.Cmyk);
            options1.setCompressionType(JpegCompressionMode.Lossless);

            // The default profiles will be used.
            options1.setRgbColorProfile(null);
            options1.setCmykColorProfile(null);

            image1.save(dataDir + "output2.jpg", options1);
        }

支持JPEG-LS图像中的2-7位每样本

Aspose.PSD for Java API支持JPEG-LS图像中的2-7位每样本。下面的代码片段演示了如何在JPEG-LS中使用该支持。

        String dataDir = Utils.getDataDir(SupportFor2And7BitsJPEG.class) + "ModifyingAndConvertingImages/";

        try (PsdImage image = (PsdImage) Image.load(dataDir + "PsdImage.psd")) {
            JpegOptions options = new JpegOptions();

            // Set 2 bits per sample to see the difference in size and quality
            byte bpp = 2;

            //Just replace one line given below in examples to use YCCK instead of CMYK
            //options.ColorType = JpegCompressionColorMode.Cmyk;
            options.setColorType(JpegCompressionColorMode.Cmyk);
            options.setCompressionType(JpegCompressionMode.JpegLs);
            options.setBitsPerChannel(bpp);

            // The default profiles will be used.
            options.setRgbColorProfile(null);
            options.setCmykColorProfile(null);

            image.save(dataDir + "2_7BitsJPEG_output.jpg", options);
        }

为JPEG图像设置ColorType和CompressionType

Aspose.PSD for Java API支持为JPEG图像设置Color Type和Compression Type，并将它们设置为灰度和渐进。下面的代码片段演示了如何使用该支持。

        String dataDir = Utils.getDataDir(ColorTypeAndCompressionType.class) + "ModifyingAndConvertingImages/";

        try (PsdImage image = (PsdImage) Image.load(dataDir + "PsdImage.psd")) {
            JpegOptions options = new JpegOptions();
            options.setColorType(JpegCompressionColorMode.Grayscale);
            options.setCompressionType(JpegCompressionMode.Progressive);

            image.save(dataDir + "ColorTypeAndCompressionType_output.jpg", options);
        }