[Digikam-devel] extragear/graphics/doc

[Gilles Caulier]

SVN commit 461937 by cgilles:

digiKam and showfoto handbook : because i'm tired to explain why digikam user must use lossless image file format, i had addes any explanations about image compression.

IMPORTANT : English words checking request !

CCMAIL: digikam-devel at kde.org

 M  +13 -0     digikam/index.docbook  
 M  +13 -0     showfoto/index.docbook  


--- trunk/extragear/graphics/doc/digikam/index.docbook #461936:461937
@@ -219,6 +219,19 @@
             </sect3>
 
             <sect3>
+            <title>Still Image Compression</title>
+    
+                <para>
+                Image compression is the application of data compression on digital images. In effect, the objective is to reduce redundancy of the image data in order to be able to store or transmit data in an efficient form.
+                </para>
+            
+                <para>
+                Image compression can be lossy or lossless. Lossless compression methods is always be preferred for high value content for archival purposes before to apply transformations like croping, resizing, color corrections, etc. This is because lossy compression methods, especially when used at low bit rates, can introduce compression artifacts. Lossy methods are especially suitable for natural images such as photos in applications where minor (sometimes imperceptible) loss of fidelity is acceptable to achieve a substantial reduction in bit rate. Lossy compression is dedicaced to publish photographs on internet. 
+                </para>
+            
+            </sect3>
+            
+            <sect3>
             <title>JPEG</title>
                 <para>
                 JPEG is a compressed format, that trades some of the image quality to keep file sizes small. In fact, most cameras save their images in this format unless you specify otherwise. A JPEG image is stored using lossy compression and you can vary the amount of compression. This allows you to choose between lower compression and higher image quality or greater compression and poorer quality. The only reason to choose higher compression is because it creates smaller file so you can store more images, and it's easier to send them by e-mail, or post them on the Web. Most cameras give you two or three choices equivalent to good, better, best although the names vary.
--- trunk/extragear/graphics/doc/showfoto/index.docbook #461936:461937
@@ -149,6 +149,19 @@
             </sect3>
 
             <sect3>
+            <title>Still Image Compression</title>
+    
+                <para>
+                Image compression is the application of data compression on digital images. In effect, the objective is to reduce redundancy of the image data in order to be able to store or transmit data in an efficient form.
+                </para>
+            
+                <para>
+                Image compression can be lossy or lossless. Lossless compression methods is always be preferred for high value content for archival purposes before to apply transformations like croping, resizing, color corrections, etc. This is because lossy compression methods, especially when used at low bit rates, can introduce compression artifacts. Lossy methods are especially suitable for natural images such as photos in applications where minor (sometimes imperceptible) loss of fidelity is acceptable to achieve a substantial reduction in bit rate. Lossy compression is dedicaced to publish photographs on internet. 
+                </para>
+            
+            </sect3>
+                        
+            <sect3>
             <title>JPEG</title>
                 <para>
                 JPEG is a compressed format, that trades some of the image quality to keep file sizes small. In fact, most cameras save their images in this format unless you specify otherwise. A JPEG image is stored using lossy compression and you can vary the amount of compression. This allows you to choose between lower compression and higher image quality or greater compression and poorer quality. The only reason to choose higher compression is because it creates smaller file so you can store more images, and it's easier to send them by e-mail, or post them on the Web. Most cameras give you two or three choices equivalent to good, better, best although the names vary.