This topic describes the basic concepts of Image Search to help you better understand and use the product.
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Instance
An instance is the basic unit of service that you purchase and use. An instance provides both computing and storage capabilities:
Computing is used to extract image features and compare similarities.
Storage is used to save the image features.
These capabilities, combined with Alibaba Cloud's proprietary image search engine, constitute the complete Image Search service. Therefore, you must create an instance before you can use Image Search.
Queries per second (QPS)
The maximum number of query requests that you can send to the Image Search API per second. A higher QPS value means that more queries can be processed in the same period. For example, if you purchase an Image Search service with 5 QPS, you can perform five image queries per second.
Queries per second is abbreviated as QPS in this topic.
Image Search QPS is divided into three types: image query QPS, image add QPS, and image delete QPS.
The image query QPS depends on your purchased plan. For example, if you purchase the 2.5 million images, 10 QPS plan, the query QPS for the instance is 10. If you purchase the 100,000 images, 1 QPS plan, the query QPS for the instance is 1.
For the image add QPS, the 100,000 images, 1 QPS plan has an image add QPS of 1. All other plans have an image add QPS of 5.
The QPS for deleting images is fixed at 20 and is not affected by your purchased plan.
Image Search is sold based on maximum image capacity and QPS, not on the number of API calls. Therefore, reports on the number of API calls for an instance are not provided.
Maximum image capacity
The maximum number of images that you can index.
The maximum image capacity is determined by your purchased plan. For example, if you purchase the 100,000 images, 1 QPS plan, the maximum image capacity for that instance is 100,000 images.
The maximum image capacity is the maximum number of images that you can index, not the number of images that you can query. Image Search does not limit the number of queries, but it does limit the QPS.
For more information about QPS limits, see Queries per second (QPS).
Image gallery
After you create or purchase an instance, you can upload images to the instance to generate a searchable image database. This database is called an image gallery.
During image upload, you can define filter conditions to set custom properties for images. During a query, you can use filter conditions to search for similar images that have a specific label. This is similar to filtering by folder.
After you upload images, you can use the Export Metadata feature to export a list of all your uploaded images.
Image import
Image import is the process of uploading images to an image gallery. There are two ways to import images:
API-based upload: You can call the Add Image API to add images. This method is suitable for adding a small number of images in real time.
Object Storage Service (OSS) import: Because Image Search integrates with Alibaba Cloud Object Storage Service (OSS), you can import images in batches from an OSS bucket to an image gallery. This method is suitable for large-scale operations that involve millions of images.
If you purchase the 100,000 images, 1 QPS plan, the real-time image add QPS for the instance is 1. For all other plans, the real-time image add QPS is 5.
For real-time image adding, you can test the feature in the management console. For more information, see Add images. We recommend that you use the official Image Search software development kit (SDK) to make API calls. For more information, see Java SDK.
To use OSS import, the OSS bucket and your purchased instance must be in the same region. For example, if the OSS bucket is in the Hangzhou region, the Image Search instance must also be in the Hangzhou region to use the OSS import feature. If the bucket and instance are in different regions, this feature is unavailable.
OSS import is a free service provided by Image Search, and its QPS is much higher than that of API-based upload. We recommend that you use the OSS import method if you have many images. For instructions on how to use OSS import, see Batch operations.
Product category
For product image search, you can choose whether to specify a product category when you add or search for images. If you specify a category, the system uses that category. If you do not specify a category, the system automatically predicts one. The prediction result is returned in the response.
Specifying a product category can narrow the search scope and improve search accuracy.
For a list of categories supported by product image search, see Category reference.
To learn how to use product categories, see the request parameters for image import and image search.
Subject identification
Subject identification improves search performance by filtering out irrelevant background information during the add and search processes.
You can choose whether to enable subject identification when you add or search for images:
If you enable subject identification, the system adds or searches for images based only on the identified subject.
If you do not enable subject identification, the system adds or searches based on the entire image.
The subject identification feature is enabled by default in Image Search. For more information, see the request parameters for image import and image search.
Product image search, generic image search, industrial hardware image search, furniture and home goods image search, and trademark image search all support the subject identification feature.
Fabric image search and copyright image search do not support the subject identification feature.
Filter condition
A condition that limits the scope of an image search. You can use filter conditions with image properties to perform searches with combined conditions using the AND and OR operators.
For instructions on how to use filter conditions, see Filter conditions.