You will need
- Adobe Photoshop
Open the image (Ctrl+O).
Using the Lasso tool (L) select the portion of hair that you want to make longer. Then copy the selection (Ctrl+J). In the menu "Edit" select "Free transform". Around the fragment will appear thin frame with markers. Pull one of them and stretch hair to the desired length. While slightly narrow fragment – so the result will be more realistic.
In the menu "Edit" select "Transformation" and then "Warp". At this time, the fragment will be superimposed a fine grid of markers. When pulling the mesh nodes, the fragment will be distorted. Deform or fragment as necessary, primarily paying attention to how realistic the result. Gravity hair should fall directly and freely. You can give them a small "wave". To accept changes, press Enter.
At the intersection of the modified fragment and the original image is formed very noticeable sharp transition. To get rid of it, take the Eraser tool quite a large size with soft edges and a pressing force and an opacity of not more than 20 percent. Work through the tool joint of the layers, until it becomes invisible.
The last step is to add shadows. If this is not done, the hair will look unnatural. Create a layer under the current one. To do this, open the layers panel by pressing F7, select the first layer and press Ctrl+J. Then take the eyedropper tool the color of the shadow in the photo, and a brush with soft edges and an opacity of about 60 percent, apply the shadow from the hair.
The drawback of this method is that it is difficult to connect the ends of your hair, so avoid this. To not show the tips of the hair, you can crop the photo or close the hair with your hand or any object. If your hair needs to be mandatory, you have to really enlarge the photo and cut out almost every hair, and then to stitch them, smoothing the joints and adjusting the hue, brightness and contrast. But the alternative is worse: you will either have to paint the hair yourself, or take them with some other pictures. In the first case, it is extremely difficult to achieve realism, and in the second case it will be clearly hair that does not belong to the person in the picture.