Workflow: Updating the pixel data in an ST_Raster value

Complexity: Intermediate Data Requirement: Use your own data Goal: Learn two ways to fetch ST_PixelData from an ST_Raster value, edit it, and write the edited pixels back to the ST_Raster value.

The pixel data editing workflow involves the following:

  1. Fetching the ST_PixelData from an ST_Raster value
  2. Editing the pixels of the ST_PixelData
  3. Writing the edited pixels of the ST_PixelData back to the ST_Raster value

You can fetch the ST_PixelData into a variable or insert it into a pixel table. If you fetch the value into a variable, all three steps can be done as part of the same SQL statement. If you insert the value to a table, the value is preserved, allowing you to do the steps of the workflow separately.

To complete this workflow, use the ST_Raster getPixelData function to fetch the ST_PixelData from the ST_Raster value, and use the ST_Raster mosaic function to write it back.

Updating an ST_Raster value with a temporary ST_PixelData variable

You can declare an ST_PixelData variable, then use the getPixelData function to fetch the ST_PixelData from an ST_Raster value into the variable.

Steps:
  1. Declare a variable, fetch the pixel data into the variable, edit the pixels, then mosaic the altered values back to the ST_Raster value.

    In these examples, the ST_PixelData value is fetched from the ST_Raster column of the urban_area table, inserted into an ST_PixelData variable, edited, and mosaicked back to the ST_Raster value.

    Oracle

    --Define the variable.
    DECLARE
      p sde.st_pixeldata;
    
    --Fetch the ST_PixelData from the urban_area table into the variable.
    BEGIN
       SELECT t.raster.getPixelData() INTO p
       FROM URBAN_AREA t
       WHERE t.raster.rasterid = 1;
    
    --Reset pixel values
       FOR i IN 1..256 LOOP
         FOR j IN 1..256 LOOP
           IF(p.getvalue(1,i,j)=0) THEN
            p.setvalue(1,i,j,100);
           END IF;
         END LOOP;
       END LOOP;
    
    --Mosaic the altered pixels to the urban_area table.
       UPDATE URBAN_AREA t
         SET raster = t.raster.mosaic(p,'compression=lz77,level=-1,nearest')
         WHERE t.raster.raster_id = 1;
    END;
    /

    PostgreSQL

    --Drop the variable (function) if it already exists.
    DROP FUNCTION IF EXISTS edit_pixeldata();
    
    --Define a varaible.
    CREATE OR REPLACE FUNCTION edit_pixeldata()
    RETURNS integer AS '
    DECLARE p st_pixeldata;
    
    --Fetch the ST_PixelData from the urban_area table into the variable.
    BEGIN
       SELECT getPixelData(raster) INTO p
       FROM urban_area
       WHERE raster_id(raster) = 1;
       
    --Reset pixel values
       FOR i IN 1..256 LOOP
         FOR j IN 1..256 LOOP
           IF(getvalue(p,1,i,j)=0) THEN
              p := setvalue(p,1,i,j,100);
           END IF;
         END LOOP;
       END LOOP;
    
    --Mosaic the altered pixels to the urban_area table.
    UPDATE urban_area
     SET raster = mosaic(raster,p,''compression=lz77,level=-1,nearest'')
     WHERE raster_id(raster) = 1;
    END;'
    LANGUAGE plpgsql;
    
    --Drop the variable.
    SELECT edit_pixeldata();
    DROP FUNCTION IF EXISTS edit_pixeldata();

    SQL Server

    --Define the variable.
    DECLARE @p ST_PIXELDATA, @i int, @j int;
    
    --Fetch the ST_PixelData from the urban_area table into the variable.
    SET @p = (SELECT raster.getPixelData(NULL)
              FROM raster.urban_area 
              WHERE raster.raster_id = 1);
    
    --Reset pixel values.
    WHILE( @i<256)
    BEGIN
      WHILE(@j<256)
      BEGIN
        IF(@p.getValue(1,@i,@j)=0)
          SELECT @p = @p.setValue(1,@i,@j,100)
        SET @j=@j+1
      END 
      SET @i=@i+1 
    END
    
    --Mosaic the altered pixels to the urban_area table
    UPDATE raster.urban_area 
    SET raster = raster.mosaic(NULL,@p,'compression=lz77,level=-1,nearest')
    WHERE raster.raster_id = 1;

Updating an ST_Raster value with a persistent ST_PixelData column

You can fetch the ST_PixelData value into a table, edit it, then mosaic it back to the ST_Raster value. This is done in three separate steps.

You might do this if you need to preserve the fetched value in the second table.

Steps:
  1. Create a table to store the pixel data value.

    In these examples, a table named pixels is created.

    Oracle

    CREATE TABLE pixels 
    (pdata sde.ST_PixelData);
    

    PostgreSQL

    CREATE TABLE pixels
    (pdata sde.ST_PixelData);

    SQL Server

    CREATE TABLE pixels
    (pdata dbo.ST_PixelData);
  2. Use the getPixelData function inside an INSERT statement to fetch the ST_PixelData to a pixel column in the pixels table.

    In these examples, the ST_PixelData value is fetched into the pixels table.

    Oracle

    INSERT INTO pixels (pdata)
       SELECT t.raster.getPixelData(), t.raster.raster_id 
       FROM urban_area t
       WHERE t.raster.raster_id = 1;
    

    PostgreSQL

    INSERT INTO pixels (pdata)
       SELECT getPixelData(raster,'level=1')
       FROM urban_area
       WHERE raster_id(raster) = 1;

    SQL Server

    INSERT INTO pixels (pdata)
       SELECT raster.getPixelData('level=1')
       FROM urban_area
       WHERE raster.raster_id = 1;
  3. Fetch the value from the pixels table to a variable, update the pixel values, then place the altered values back in the pixels table.

    Oracle

    DECLARE
    p sde.st_pixeldata;
    BEGIN
      
        SELECT pdata INTO p FROM PIXELS; 
        FOR i IN 1..256 LOOP
          FOR j IN 1..256 LOOP
            IF(p.getvalue(1,i,j)=0) THEN
              p.setvalue(1,i,j,100);
            END IF;
          END LOOP;
        END LOOP;
    
        UPDATE PIXELS t 
        SET pdata = p;
    END;
    /

    PostgreSQL

    DROP FUNCTION EXISTS edit_pixels();
    CREATE OR REPLACE FUNCTION EDIT_PIXELS()
    RETURNS void AS '
    DECLARE p st_pixeldata;
    BEGIN
      SELECT pdata INTO p 
      FROM pixels; 
      FOR i IN 1..256 LOOP
        FOR j IN 1..256 LOOP
          IF(getvalue(p,1,i,j)=0) THEN
             p := setvalue(p,1,i,j,100);
          END IF;
        END LOOP;
      END LOOP;
      UPDATE pixels SET pdata = p;
    END;' LANGUAGE plpgsql;

    SQL Server

    DECLARE
    @p sde.st_pixeldata, @i int, @j int;
    SET @p = (SELECT pdata FROM pixels);
    SET @i = 0;
    SET @j = 0;
    WHILE (@i<256)
    BEGIN
        WHILE (@j<256)
        BEGIN
          IF(@p.getValue(1,@i,@j)=0)
              SELECT @p=@p.setValue(1,@i,@j,100);
            SET @j=@j+1
        END
        SET @i=@i+1
    END
    UPDATE raster.pixels SET pdata = @p;
  4. Mosaic the altered values from the pixels table to the ST_Raster value in the urban_area table.

    Oracle

    DECLARE
    p sde.st_pixeldata;
    BEGIN
      
      SELECT pdata INTO p FROM PIXELS; 
    
      UPDATE URBAN_AREA t 
      SET raster = t.raster.mosaic(p,'compression=lz77,level=-1,nearest')
      WHERE t.raster.raster_id = 1; 
    
    END;
    /

    PostgreSQL

    SELECT edit_pixels();
    
    DROP FUNCTION IF EXISTS edit_pixels();
    
    DROP FUNCTION IF EXISTS update_pixels();
    
    CREATE OR REPLACE FUNCTION UPDATE_PIXELS()
    RETURNS void AS '
    DECLARE p st_pixeldata;
    BEGIN
      SELECT pdata INTO p FROM pixels; 
      UPDATE urban_area t 
      SET raster = mosaic(raster,p, ''compression=lz77,level=-1,nearest'')
      WHERE raster_id(raster) = 1; 
    END;' LANGUAGE plpgsql;
    
    SELECT update_pixels();
    
    DROP FUNCTION IF EXISTS update_pixels();

    SQL Server

    DECLARE @p sde.ST_Pixeldata;
    SET @p = (SELECT pdata FROM pixels);
    UPDATE raster.urban_area 
    SET raster = raster.mosaic(NULL,@p,'compression=lz77,level=-1,nearest')
    WHERE raster.raster_id = 1;

Related Topics


2/5/2013