ST_AsJPEG
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## Name

ST_AsJPEG — Return the raster tile selected bands as a single Joint Photographic Exports Group (JPEG) image (byte array). If no band is specified and 1 or more than 3 bands, then only the first band is used. If only 3 bands then all 3 bands are used and mapped to RGB.

## Synopsis

`bytea ST_AsJPEG(`raster rast, text[] options=NULL`)`;

`bytea ST_AsJPEG(`raster rast, integer nband, integer quality`)`;

`bytea ST_AsJPEG(`raster rast, integer nband, text[] options=NULL`)`;

`bytea ST_AsJPEG(`raster rast, integer[] nbands, text[] options=NULL`)`;

`bytea ST_AsJPEG(`raster rast, integer[] nbands, integer quality`)`;

## Description

Returns the selected bands of the raster as a single Joint Photographic Exports Group Image (JPEG). Use ST_AsGDALRaster if you need to export as less common raster types. If no band is specified and 1 or more than 3 bands, then only the first band is used. If 3 bands then all 3 bands are used. There are many variants of the function with many options. These are itemized below:

- `nband` is for single band exports.

- `nbands` is an array of bands to export (note that max is 3 for JPEG) and the order of the bands is RGB. e.g ARRAY[3,2,1] means map band 3 to Red, band 2 to green and band 1 to blue

- `quality` number from 0 to 100. The higher the number the crisper the image.

- `options` text Array of GDAL options as defined for JPEG (look at create_options for JPEG ST_GDALDrivers). For JPEG valid ones are `PROGRESSIVE` ON or OFF and `QUALITY` a range from 0 to 100 and default to 75. Refer to GDAL Raster format options for more details.

Availability: 2.0.0 - requires GDAL >= 1.6.0.

## Examples: Output

    -- output first 3 bands 75% quality
    SELECT ST_AsJPEG(rast) As rastjpg
        FROM dummy_rast WHERE rid=2;

    -- output only first band as 90% quality
    SELECT ST_AsJPEG(rast,1,90) As rastjpg
        FROM dummy_rast WHERE rid=2;

    -- output first 3 bands (but make band 2 Red, band 1 green, and band 3 blue, progressive and 90% quality
    SELECT ST_AsJPEG(rast,ARRAY[2,1,3],ARRAY['QUALITY=90','PROGRESSIVE=ON']) As rastjpg
        FROM dummy_rast WHERE rid=2;

## See Also

Section 11.3, “Building Custom Applications with PostGIS Raster”, ST_GDALDrivers, ST_AsGDALRaster, ST_AsPNG, ST_AsTIFF

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