[jira] [Commented] (IMAGING-94) Add ability to load partial TIFF images

["Damjan Jovanovic (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/IMAGING-94?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13483490#comment-13483490 ] 

Damjan Jovanovic commented on IMAGING-94:
-----------------------------------------

Hi Gary

Wow what a patch :).

In this section, is there some reason you don't use System.arraycopy()? That should be even faster than looping and copying 2 values at a time.

{code}
+        // Transcribe the data.  In this code block, there is a small
+        // amount of loop unrolling.  In testing, unrolling saves about 25 
+        // percent load time for large subimages.  2/3 of the cost of reading
+        // the subimage is in the transcription of data.
+        int[] argb = new int[w * h];
+        int k = 0;
+        int w2 = w / 2;
+        for (int iRow = 0; iRow < h; iRow++) {
+            int dIndex = (iRow + y) * width + x;
+            for (int j = 0; j < w2; j++) {
+                argb[k++] = this.data[dIndex++];
+                argb[k++] = this.data[dIndex++];
+            }
+            if ((w & 1) != 0) {
+                // there's an odd number of columns
+                argb[k++] = this.data[dIndex++];
+            }
+        }
{code}
                
> Add ability to load partial TIFF images
> ---------------------------------------
>
>                 Key: IMAGING-94
>                 URL: https://issues.apache.org/jira/browse/IMAGING-94
>             Project: Commons Imaging
>          Issue Type: New Feature
>          Components: Format: TIFF
>            Reporter: Gary Lucas
>         Attachments: LucasTrackerItem94_Oct14.patch
>
>
> For most Apache Commons Imaging applications, the easiest way to obtain a sub image from a file is to simply use the Imaging class to load it as a BufferedImage and then use BufferedImage’s getSubimage() method to extract the portion of the image you wish to use.  The TIFF format presents a special problem because it is very common to have huge images (100’s or even 1000’s of megapixel).  Examples include Landsat satellite images, global-scale GeoTIFF images, etc.  In such cases, loading the entire image into memory is not practical because it would require too much memory.  For example, I am currently working with a 21600 by 10800 image that requires more than 890 megabytes to store as a BufferedImage.  That value is pushing the limit of what I can configure Java to handle on my particular OS.
> I propose to implement features for TIFF files that would permit Commons Imaging to load a partial image of a TIFF file using only the amount memory actually needed to hold the sub-image.
> These changes would not interfere with normal operations of TIFF files and would not affect other image formats.  If there were a need for similar features for other image formats, they could be phased in through future changes.
> The specification for a sub-image would be through the use of the params argument in the getBufferedImage call as follows:
>         HashMap<String, Object> params = new HashMap<String, Object>();
>         params.put(TiffConstants.PARAM_KEY_SUBIMAGE_X, new Integer( x ));
>         params.put(TiffConstants.PARAM_KEY_SUBIMAGE_Y, new Integer( y ));
>         params.put(TiffConstants.PARAM_KEY_SUBIMAGE_WIDTH, new Integer(width));
>         params.put(TiffConstants.PARAM_KEY_SUBIMAGE_HEIGHT, new Integer(height));

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