Enlightenment CVS committal
Author : technikolor
Project : e17
Module : docs
Dir : e17/docs/cookbook/xml
Modified Files:
imlib_recipes.xml
Log Message:
Watermark recipe.
===================================================================
RCS file: /cvsroot/enlightenment/e17/docs/cookbook/xml/imlib_recipes.xml,v
retrieving revision 1.5
retrieving revision 1.6
diff -u -3 -r1.5 -r1.6
--- imlib_recipes.xml 4 Jul 2004 00:17:34 -0000 1.5
+++ imlib_recipes.xml 6 Jul 2004 09:27:02 -0000 1.6
@@ -55,68 +55,84 @@
</para>
<section>
-<title>Recipe: Example</title>
+<sectioninfo>
+ <author>
+ <firstname>Ben</firstname>
+ <surname>Rockwood</surname>
+ <email>[EMAIL PROTECTED]</email>
+ <othername>technikolor</othername>
+ </author>
+ <date>6 July 2004</date>
+</sectioninfo>
+
+<title>Recipe: Image watermarking</title>
+
<para>
-This is the first paragraph of the recipe.
+With so many individuals putting so many images online its easy to forget where they
+came from and hard ensure that copyrighted material isn't inadvertantly misused.
Simply
+adding a watermark image such as your sites logo to each of your images can solve
both
+these problems. But adding watermarks manual is a long and repetative task. Imlib2
can
+easily be used to solve this problem. What we need to do is take an input image,
+and then specify a watermark image (your logo), position the watermark on the input
image
+and then save it out to a new image which we'll use on the site. The apps would look
+something like this:
</para>
<example>
<title>Imlib2 WaterMark Program</title>
<programlisting>
#define X_DISPLAY_MISSING
-#include >Imlib2.h<
-#include >stdio.h<
+#include <Imlib2.h>
+#include <stdio.h>
int main(int argc, char **argv){
- Imlib_Image image_input, image_watermark, image_output;
- int w_input, h_input;
- int w_watermark, h_watermark;
- char watermark[] = "watermark.png";
-
- if(argc $lt; 1) {
- printf("Input image is: %s\n", argv[1]);
- printf("Watermark is: %s\n", watermark);
- }
- else {
- printf("Usage: %s input_image output_imagename\n", argv[0]);
- exit(1);
- }
-
-
-
- image_input = imlib_load_image(argv[1]);
- if(image_input) {
- imlib_context_set_image(image_input);
- w_input = imlib_image_get_width();
- h_input = imlib_image_get_height();
- printf("Input size is: %d by %d\n", w_input, h_input);
- image_output = imlib_clone_image();
- }
-
- image_watermark = imlib_load_image(watermark);
- if(image_watermark) {
- imlib_context_set_image(image_watermark);
- w_watermark = imlib_image_get_width();
- h_watermark = imlib_image_get_height();
- printf("WaterMark size is: %d by %d\n", w_watermark, h_watermark);
- /* Modify alpha of watermark by half */
-
- }
-
- if(image_output) {
- int dest_x, dest_y;
-
- dest_x = w_input - w_watermark;
- dest_y = h_input - h_watermark;
- imlib_context_set_image(image_output);
-
- /* Src Image is watermark, destination is clone */
- imlib_blend_image_onto_image(image_watermark, 0, 0, 0, w_watermark,
h_watermark, dest_x, dest_y, w_watermark, h_watermark);
- imlib_save_image(argv[2]);
- printf("Wrote watermarked image to filename: %s\n", argv[2]);
- }
+ Imlib_Image image_input, image_watermark, image_output;
+ int w_input, h_input;
+ int w_watermark, h_watermark;
+ char watermark[] = "watermark.png";
+
+ if(argc < 1) {
+ printf("Input image is: %s\n", argv[1]);
+ printf("Watermark is: %s\n", watermark);
+ }
+ else {
+ printf("Usage: %s input_image output_imagename\n", argv[0]);
+ exit(1);
+ }
+
+ image_input = imlib_load_image(argv[1]);
+ if(image_input) {
+ imlib_context_set_image(image_input);
+ w_input = imlib_image_get_width();
+ h_input = imlib_image_get_height();
+ printf("Input size is: %d by %d\n", w_input, h_input);
+ image_output = imlib_clone_image();
+ }
+
+ image_watermark = imlib_load_image(watermark);
+ if(image_watermark) {
+ imlib_context_set_image(image_watermark);
+ w_watermark = imlib_image_get_width();
+ h_watermark = imlib_image_get_height();
+ printf("WaterMark size is: %d by %d\n",
+ w_watermark, h_watermark);
+ }
+
+ if(image_output) {
+ int dest_x, dest_y;
+
+ dest_x = w_input - w_watermark;
+ dest_y = h_input - h_watermark;
+ imlib_context_set_image(image_output);
+
+ imlib_blend_image_onto_image(image_watermark, 0,
+ 0, 0, w_watermark, h_watermark,
+ dest_x, dest_y, w_watermark, h_watermark);
+ imlib_save_image(argv[2]);
+ printf("Wrote watermarked image to filename: %s\n", argv[2]);
+ }
return(0);
@@ -126,8 +142,30 @@
</example>
<para>
-Another paragraph. Don't forget to replace less-than and greater-than
-symbols with the proper < and > even in your program listings.
+Looking at the example, we first do some really basic argument checking, accepting an
input impage as the first argument
+and an output image name for our watermarked copy.
+Using <command>imlib_load_image()</command> we load the input image and then grab its
dimentions using the get functions.
+The <command>imlib_clone_image()</command> function we can create a copy of the input
image, which will be the base of out
+watermarked output. Next se load the watermark image, and notice that then use
<command>imlib_context_set_image()</command>
+to change the context from the input image (image_input) to the watermark image
(image_watermark). Now we grab it's
+dimensions as well. In the final block we do two simple calculations to determine
the positioning of the watermark on the
+output image, in this case I want the watermark on the bottom right-hand corner. The
magic function that really does the
+work in this program is <command>imlib_blend_image_onto_image()</command>. Notice
that we change context to the output
+image before proceeding. The blend function will, as the name suggests, blend two
images together which we refer to
+as the source and destination image.
+The blend function blends a source image onto the current image context which we
designate as the destination.
+The arguments supplied to
+<command>imlib_blend_image_onto_image</command> can look tricky, we need to tell it
which source to use (the watermark),
+whether to merge the alpha channel (0 for no), the dimensions of the source image (x,
y, w, h) and the dimensions of the
+destination image (x, y, w, h). You'll notice that in the example the we set the x
and y positions of the source (watermark)
+image to 0 and then use the full width. The destination (input image) is set to the
bottom right hand corner minus
+the dimensions of the watermark, and then we specify the width and height of the
watermark.
+Finally, we use the <command>imlib_save_image()</command> argument to save the output
image.
+</para>
+
+<para>
+While this example should be significantly improved for real use, it outlines the
basics of Imlib2 blending
+to solves a very common problem effeciently.
</para>
</section>
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