Changes between Version 34 and Version 35 of WKTRaster/SpecificationWorking01

Timestamp:

Dec 11, 2009, 9:06:30 AM (14 years ago)

Author:

pracine

Comment:

—

WKTRaster/SpecificationWorking01

@@ -200 +200 @@
 
 '''ST_Band(raster, band) -> raster'''[[BR]]
-Return a single band from a multiband raster. If "band" is greater than the value returned by ST_GetNumBands(), the function returns the last band. This function should be used to select a band before converting it to JPEG, TIFF, PNG, SVG or KML with the corresponding function. e.g. '''ST_AsJPEG(ST_Band(raster, band), quality)
-
+Return a single band from a multiband raster. If "band" is greater than the value returned by ST_GetNumBands(), the function returns the last band. This function should be used to select a band before converting it to JPEG, TIFF, PNG, SVG or KML with the corresponding function. e.g. '''ST_AsTIFF(ST_Band(raster, band))
+
+----
 '''ST_AsJPEG(raster, quality) -> JPEG as "bytea"'''[[BR]]
 Return the raster as a JPEG encoded as a PostgreSQL bytea. By default quality is set to 75, but this option can be used to select other values. Values must be in the range 10-100. Low values result in higher compression ratios, but poorer image quality. Values above 95 are not meaningfully better quality but can but substantially larger. (copied from http://www.gdal.org/frmt_jpeg.html)
 
-----
+
 '''Open Question:''' Is JPEG export limited to raster having 8 bit unsigned integer pixeltype (8BUI)?
 
@@ -229 +230 @@
 mloskot: ATM, I have no thoughts on this issue.
 
-----
 '''Open Question:''' Is JPEG export limited to raster having 1 or 3 bands?
 
@@ -237 +237 @@
 
 mloskot: I agree, the answer should be yes.
+
+'''Here is an attempt to define the different versions of the function:'''
+
+The most minimalistic versions of the function should assume band 1, 2 and 3 as being r, g, b and the quality equal to 75:
+
+ST_AsJPEG(raster) -quality = 75
+
+A variant allow specifying the quality:
+
+ST_AsJPEG(raster, integer)
+
+Another variant should enable us to specify which band correspond to the r, the g and the b:
+
+ST_AsJPEG(raster, integer, integer, integer) - raster, rband, gband, bband, quality=75
+ST_AsJPEG(raster, integer, integer, integer, integer) - raster, rband, gband, bband, quality
+
+Another version should be designed to be used with a future ST_Band(raster) function. In this case there is no attempt to extract r, g or b band from any passed raster:
+
+ST_AsJPEG(raster, raster, raster) and ST_AsJPEG(raster, raster, raster, quality)
+
+Another series should allow converting 1 band raster with pixel of type 8BUI to a grayscale JPEG:
+
+ST_AsJPEG(raster, "GRAYSCALE") - convert only band 1 with quality = 75
+ST_AsJPEG(raster, "GRAYSCALE", integer) - convert only band 1 with specified quality
+ST_AsJPEG(raster, integer, "GRAYSCALE") - allow specifying the band number to convert 
+ST_AsJPEG(raster, integer, "GRAYSCALE", integer) - allow specifying the band number to convert and the quality
+
+Another series should allow converting 1 band raster of ANY pixel type to a grayscale JPEG. Pixel types different than 8BUI should be mapped according to specified min, max values and a mapping mode: "MaxMinValue" (default) or "MaxMinType".
+
+ST_AsJPEG(raster, "GRAYSCALE", min, max, text) - convert only band 1 with quality = 75
+ST_AsJPEG(raster, "GRAYSCALE", integer, min, max, text) - convert only band 1 with specified quality
+ST_AsJPEG(raster, integer, "GRAYSCALE", min, max, text) - allow specifying the band number to convert 
+ST_AsJPEG(raster, integer, "GRAYSCALE", integer, min, max, text) - allow specifying the band number to convert and the quality
+
+
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