I want to save small images in my room database and I have two issues:
How do I save an image in my database?
How do I save multiple images in my database?
I tried saving a bitmap in the way recommended by the developers page (https://developer.android.com/training/data-storage/room/defining-data)
#Parcelize
#Entity(tableName = "image_table")
data class ImgMod(
#PrimaryKey(autoGenerate = true)
var invoiceId: Long = 0L,
#ColumnInfo(name = "image")
var single_img: Bitmap?
): Parcelable
However, I receive the following error:
Cannot figure out how to save this field into database. You can consider adding a type converter for it.
Secondly, I would like to save multiple images in one database entry. But I receive the same error with the following snippets:
#ColumnInfo(name = "imageList")
var img_list: ArrayList<BitMap>
or decoded bitmap as a String
#ColumnInfo(name = "imageList")
var decoded_img_list: ArrayList<String>
I am sorry if this is a very basic question. But how do I have to configure the database/process the data to an image list?
Thank you in advance,
rot8
A very simple way to get images into the database (although I personally discourage it) would be to base-64 encode the bitmaps into a String and put it into a row of the database.
Take in account that bitmaps are very memory heavy; and base64 encoding something increases it's size some more so be careful when loading a bunch of images... I do also think Room and SQLite supports binary data as blobs, so you could just declare a column as ByteArray and it should just work.
What I've been doing in my projects is to write them into the internal or external storage of my app and then store the reference Uri as a String to later be able to retrieve the image from disk.
Something that I discourage even more is to stuff more than one value per row; having a list of stuff inside a coulmn in SQL is definetely not a pattern you should follow. Creating a "join" table should be simple enough or simply an extra column you could use to group them by should be easy enough, right?
Related
i´m currently building a Flutter app that includes a larger set of data (like 2000-10000 pieces of text).
I´m relatively new to Flutter delevopment so i have no idea what databases are the best for this case.
The app needs no connection to the internet a all data is on the device after downloading.
You only need to query this data extensively and build now datasets out of it.
I researched a bit, but the most common used database (hive) seems not to be suitable for my needs.
If anyone could help, I´d appreciate it.
It seems ObjectBox is best For Large Data ,it Performs very Well
[Check this package best suits for your data][1]
import 'package:objectbox/objectbox.dart';
class Note {
// Each "Entity" needs a unique integer ID property.
// Add `#Id()` annotation if its name isn't "id" (case insensitive).
int id = 0;
String? text;
DateTime date;
#Transient() // Make this field ignored, not stored in the database.
int? notPersisted;
// An empty default constructor is needed but you can use optional args.
Note({this.text, DateTime? date}) : date = date ?? DateTime.now();
// Note: just for logs in the examples below(), not needed by ObjectBox.
toString() => 'Note{id: $id, text: $text}';
}```
I am new to swift but I have made an android app where a string array is selected from an xml file. This is a large xml file that contains a lot of string arrays and the app gets the relevant string array based on a user selection.
I am now trying to develop the same app for iOS using swift. I would like to use the same xml file but I can not see and easy way to get the correct array. For example, part of the xml looks like this
<string-array name="OCR_Businessstudies_A_Topics">
<item>1. Business objectives and strategic decisions</item>
<item>2. External influences facing businesses</item>
<item>3. Marketing and marketing strategies</item>
<item>4. Operational strategy</item>
<item>5. Human resources</item>
<item>6. Accounting and financial considerations</item>
<item>7. The global environment of business</item>
</string-array>
<string-array name="OCR_Businessstudies_AS_Topics">
<item>1. Business objectives and strategic decisions</item>
<item>2. External influences facing businesses</item>
<item>3. Marketing and marketing strategies</item>
<item>4. Operational strategy</item>
<item>5. Human resources</item>
<item>6. Accounting and financial considerations</item>
</string-array>
If I have the string "OCR_Businessstudies_A_Topics" how do i get the "OCR_Businessstudies_A_Topics" array from the xml file.
This is very straight forward in android and although I have used online tutorials for swift it seems like I have to parse the xml file but do not seem to be getting anywhere.
Is there a better approach than trying to parse the whole xml fie?
Thanks
Barry
You can write your own XML parser, conforming to NSXMLParser or use a library like HTMLReader:
let fileURL = NSBundle.mainBundle().URLForResource("data", withExtension: "xml")!
let xmlData = NSData(contentsOfURL: fileURL)!
let topic = "OCR_Businessstudies_A_Topics"
let document = HTMLDocument(data: xmlData, contentTypeHeader: "text/xml")
for item in document.nodesMatchingSelector("string-array[name='\(topic)'] item") {
print(item.textContent)
}
I'm trying to figure out how to populate a table from a JSON array. So far, I can populate my table cells perfectly fine by using the following code:
self.countries = [[NSArray alloc]initWithObjects:#"Argentina",#"China",#"Russia",nil];
Concerning the JSON, I can successfully retrieve one line of text at a time and display it in a label. My goal is to populate an entire table view from a JSON array. I tried using the following code, but it still won't populate my table. Obviously I'm doing something wrong, but I searched everywhere and still can't figure it out:
NSURL *url = [NSURL URLWithString:#"http://BlahBlahBlah.com/CountryList"];
NSURLRequest *request = [NSURLRequest requestWithURL:url];
AFJSONRequestOperation *operation = [AFJSONRequestOperation JSONRequestOperationWithRequest:request success:^(NSURLRequest *request, NSHTTPURLResponse *response, id JSON)
{
NSLog(#"%#",[JSON objectForKey:#"COUNTRIES"]);
self.countries = [JSON objectForKey:#"COUNTRIES"];
}
failure:nil];
[operation start];
I am positive that the data is being retrieved, because the NSLog outputs the text perfectly fine. But when I try setting my array equal to the JSON array, nothing happens. I know the code is probably wrong, but I think I'm on the right track. Your help would be much appreciated.
EDIT:
This is the text in the JSON file I'm using:
{
"COUNTRIES": ["Argentina", "China", "Russia",]
}
-Miles
It seems that you need some basic JSON parsing. If you only target iOS 5.0 and above devices, then you should use NSJSONSerialization. If you need to support earlier iOS versions, then I really recommend the open source JSONKit framework.
Having recommended the above, I myself almost always use the Sensible TableView framework to fetch all data from my web service and automatically display it on a table view. Saves me a ton of manual labor and makes app maintenance a breeze, so it's probably something to consider too. Good luck!
I'm posting this thread because I have some difficulties to deal with pictures in Java. I would like to be able to convert a picture into a byte[] array, and then to be able to do the reverse operation, so I can change the RGB of each pixel, then make a new picture. I want to use this solution because setRGB() and getRGB() of BufferedImage may be too slow for huge pictures (correct me if I'm wrong).
I read some posts here to obtain a byte[] array (such as here) so that each pixel is represented by 3 or 4 cells of the array containing the red, the green and the blue values (with the additional alpha value, when there are 4 cells), which is quite useful and easy to use for me. Here's the code I use to obtain this array (stored in a PixelArray class I've created) :
public PixelArray(BufferedImage image)
{
width = image.getWidth();
height = image.getHeight();
DataBuffer toArray = image.getRaster().getDataBuffer();
array = ((DataBufferByte) toArray).getData();
hasAlphaChannel = image.getAlphaRaster() != null;
}
My big trouble is that I haven't found any efficient method to convert this byte[] array to a new image, if I wanted to transform the picture (for example, remove the blue/green values and only keeping the red one). I tried those solutions :
1) Making a DataBuffer object, then make a SampleModel, to finally create a WritableRaster and then BufferedImage (with additional ColorModel and Hashtable objects). It didn't work because I apparently don't have all the information I need (I have no idea what's the Hashtable for BufferedImage() constructor).
2) Using a ByteArrayInputStream. This didn't work because the byte[] array expected with ByteArrayInputStream has nothing to do with mine : it represents each byte of the file, and not each component of each pixel (with 3-4 bytes for each pixel)...
Could someone help me?
Try this:
private BufferedImage createImageFromBytes(byte[] imageData) {
ByteArrayInputStream bais = new ByteArrayInputStream(imageData);
try {
return ImageIO.read(bais);
} catch (IOException e) {
throw new RuntimeException(e);
}
}
I have tried the approaches mentioned here but for some reason neither of them worked. Using ByteArrayInputStream and ImageIO.read(...) returns null, whereas byte[] array = ((DataBufferByte) image.getRaster().getDataBuffer()).getData(); returns a copy of the image data, not a direct reference to them (see also here).
However, the following worked for me. Let's suppose that the dimensions and the type of the image data are known. Let also byte[] srcbuf be the buffer of the data to be converted into BufferedImage. Then,
Create a blank image, for example
img=new BufferedImage(width, height, BufferedImage.TYPE_3BYTE_BGR);
Convert the data array to Raster and use setData to fill the image, i.e.
img.setData(Raster.createRaster(img.getSampleModel(), new DataBufferByte(srcbuf, srcbuf.length), new Point() ) );
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_3BYTE_BGR);
byte[] array = ((DataBufferByte) image.getRaster().getDataBuffer()).getData();
System.arraycopy(pixelArray, 0, array, 0, array.length);
This method does tend to get out of sync when you try to use the Graphics object of the resulting image. If you need to draw on top of your image, construct a second image (which can be persistant, i.e. not constructed every time but re-used) and drawImage the first one onto it.
Several people upvoted the comment that the accepted answer is wrong.
If the accepted answer isn't working, it may be because Image.IO doesn't have support for the type of image you're trying, for example tiff images.
To make it work, you need to add an extra jar to handle the image type.
You can add jai-imageio-core-1.3.1.jar to your classpath with:
<!-- https://mvnrepository.com/artifact/com.github.jai-imageio/jai-imageio-core -->
<dependency>
<groupId>com.github.jai-imageio</groupId>
<artifactId>jai-imageio-core</artifactId>
<version>1.3.1</version>
</dependency>
To add support for:
wbmp
bmp
pcx
pnm
raw
tiff
gif (write)
You can check the list of supported formats with:
for(String format : ImageIO.getReaderFormatNames())
System.out.println(format);
Note that you only have to drop the jar (jai-imageio-core-1.3.1.jar for example) into your classpath to make it work.
Other projects that add additional support for image types include:
https://github.com/haraldk/TwelveMonkeys
https://github.com/geosolutions-it/imageio-ext
The approach by using ImageIO.read directly is not right in some cases. In my case, the raw byte[] doesn't contain any information about the width and height and format of the image. By only using ImageIO.read, It is impossible for the program to construct a valid image.
It is necessary to pass the basic information of the image to BufferedImage object:
BufferedImage outBufImg = new BufferedImage(width, height, bufferedImage.TYPE_3BYTE_BGR);
Then set the data for the BufferedImage object by using setRGB or setData. (When using setRGB, it seems we must convert byte[] to int[] first. As a result, it may cause performance issues if the source image data is big. Maybe setData is a better idea for big byte[] typed source data.)
I am trying to append 2 images (as byte[] ) in GoogleAppEngine Java and then ask HttpResponseServlet to display it.
However, it does not seem like the second image is being appended.
Is there anything wrong with the snippet below?
...
resp.setContentType("image/jpeg");
byte[] allimages = new byte[1000000]; //1000kB in size
int destPos = 0;
for(Blob savedChart : savedCharts) {
byte[] imageData = savedChart.getBytes(); //imageData is 150k in size
System.arraycopy(imageData, 0, allimages, destPos, imageData.length);
destPos += imageData.length;
}
resp.getOutputStream().write(allimages);
return;
Regards
I would expect the browser/client to issue 2 separate requests for these images, and the servlet would supply each in turn.
You can't just concatenate images together (like most other data structures). What about headers etc.? At the moment you're providing 2 jpegs butted aainst one another and a browser won't handle that at all.
If you really require 2 images together, you're going to need some image processing library to do this for you (or perhaps, as noted, AWT). Check out the ImageIO library.
Seem that you have completely wrong concept about image file format and how they works in HTML.
In short, the arrays are copied very well without problem. But it is not the way how image works.
You will need to do AWT to combine images in Java