motion photo的压缩

# motion photo/ live photo的压缩

# 判断是否为动态图

# 文件格式标准:

https://developer.android.com/media/platform/motion-photo-format?hl=zh-cn

# by xmp

按谷歌的标准,判断xmp里是否有关键标签,有了之后,提取其中关键的字段:视频文件的大小

            String androidXmp = "xmlns:GCamera=";
            String iosXmp = "iosxxx";
            if (!xmp.contains(androidXmp) && !xmp.contains(iosXmp)) {
                return false;
            }
            if (xmp.contains(androidXmp)) {
                LogUtils.d("读取xmp",xmp);
                    String regex0 = "GCamera:MicroVideoOffset=\"(\\d+)\"";
                    // 创建 Pattern 对象
                    Pattern pattern0 = Pattern.compile(regex0);
                    // 创建 matcher 对象
                    Matcher matcher0 = pattern0.matcher(xmp);
                    // 查找并提取数字
                    if (matcher0.find()) {
                        String number = matcher0.group(1);
                        int length = Integer.parseInt(number);
                        System.out.println("提取到的数字是: " + number);

                        if (wholeFileLength <= length) {
                            System.out.println("文件大小小于视频文件大小, xmp显示是动态图,但实际不是 " + fileOrUriPath);
                            return false;
                        }
                        //提取视频文件
                        if (extractVideo) {
                            extractMp4FromMotionPhoto(fileOrUriPath, motion.mp4CacheFile(fileOrUriPath), wholeFileLength - length, length);
                        }

                        return true;
                    } else {
                        String regex = "<Container:Item\\s+Item:Mime=\"video/mp4\"\\s+Item:Semantic=\"MotionPhoto\"\\s+Item:Length=\"(\\d+)\"\\s+Item:Padding=\"(\\d+)\"\\s*/>";
                        Pattern pattern = Pattern.compile(regex);
                        Matcher matcher = pattern.matcher(xmp);
                        if (matcher.find()) {
                            String length = matcher.group(1);
                            String padding = matcher.group(2);
                            System.out.println("length: " + length + ", padding:" + padding);
                            int len = Integer.parseInt(length);
                            int pad = Integer.parseInt(padding);
                            if (wholeFileLength <= len + pad) {
                                System.out.println("文件大小小于视频文件大小2, xmp显示是动态图,但实际不是 " + fileOrUriPath);
                                return false;
                            }
                            //提取视频文件
                            if (extractVideo) {
                                extractMp4FromMotionPhoto(fileOrUriPath, motion.mp4CacheFile(fileOrUriPath), wholeFileLength - (len + pad), len);
                            }
                            return true;

                        } else {
                            LogUtils.w("没有找到xmp里匹配的模式。");
                        }
                }
            }else {
                LogUtils.w("没有找到xmp里匹配的模式2");
            }

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# by byte:

最准确,且不受于不同版本的协议差异影响

但是需要逐个比对字节,io耗时较多

文件结尾:

mp4文件头格式:

# 压缩前后:

分别对图片和视频都做了压缩,rotation/orientation不为0的,还对原图和原视频做了旋转处理并将rotation//orientation置为0

xmp为空的,将视频文件大小写入到motion photo模板中:

public static final String xmpTmplate = "<x:xmpmeta xmlns:x=\"adobe:ns:meta/\" x:xmptk=\"Adobe XMP Core 5.1.0-jc003\">" +
            "  <rdf:RDF xmlns:rdf=\"http://www.w3.org/1999/02/22-rdf-syntax-ns#\">" +
            "<rdf:Description rdf:about=\"\"" +
            "xmlns:GCamera=\"http://ns.google.com/photos/1.0/camera/\"" +
            "xmlns:MiCamera=\"http://ns.xiaomi.com/photos/1.0/camera/\"" +
            "GCamera:MicroVideoVersion=\"1\"" +
            "GCamera:MicroVideo=\"1\"" +
            "GCamera:MicroVideoOffset=\"xxxxxx\"" +
            "GCamera:MicroVideoPresentationTimestampUs=\"900999\"" +
            "MiCamera:XMPMeta=\"&lt;?xml version='1.0' encoding='UTF-8' standalone='yes' ?&gt;\"/>" +
            " </rdf:RDF>" +
            "</x:xmpmeta>";