I would like increase the height of a part of my image.
Here is my current image:
I would like increase the height with 90px here: http://prntscr.com/5viaqk
Not the bottom line.
Firstly, increase the size of your canvas by 90 pixels probably aligning to the top would be a good idea:
Now select and move the bottom line to new bottom of the canvas. Now, this is where you have a slight problem. Both the bottom line in your image and the area which you wish to increase have a subtle angular texture (for want of a better description). I've exaggerated it here:
If you really want to have that in your final image, I'd be tempted to redraw the whole image, if you don't have access to the original. Draw the triangles with different greys, add a noise layer and a slight gradient, place that in a group, change the opacity and you're pretty much there.
Step 1 : open your image in Adobe Photoshop
Step 2 : In case for this particular image , Make layer in background , fill with white color, and merge the layers for better result PREVIEW
Step 3 : Go to Image menu for canvas size or press CTR + ALT + C and type what particular height you need to increase
Step 4 : Lock canvas from bottom and HIT ok to increase canvas size from top
Step 5 : now select your image from the particular top you want to increase
Step 6 : Press CTR + T for transformation and increase your image size till the canvas.
For more detail solution watch this video : http://goo.gl/c7B8Tr