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| ![[no author]](../../common/images/transpix.gif)  by Phillip Ross <phil(at)ryoo.cis.pitt.edu> Content: | 
| Graphical Photocomposition with The Gimp![[Illustration]](../../common/images/transpix.gif)  Abstract: 
    There is no better way to learn than by example. The authors
    show us a very simple photocomposition technique using
    Photoshop & The Gimp. Now you have
    a chance to compare both tools.
    
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The GNU Image Manipulation Program (AKA The GIMP) has been in developement for quite awhile and early versions left a lot to be desired. GIMP has since come a long long way and is far more powerful than the early versions. Those who were turned off by the short comings of the first versions are highly encouraged to test out some of newest versions in the 0.99.xx series. I hope to demonstrate that GIMP is very much a viable tool for doing professional graphics.
This article is the first in a series of articles that will show how one can use GIMP to achieve the same effects as one is capable of doing with Adobe Photoshop. Juan Manuel Sepulveda will be demonstrating some nice effects an artist can achieve with Photoshop, and I will show how to do the same thing with GIMP. In his first article he puts together a cute scene starring Daniel, his nephew. We will probably concentrate in our first few articles on explaining how to build this scene with Photoshop and Gimp. My article below explains specificly how to use GIMP to isolate Daniel from the rest of the background in the image.
Warning:You must have a steady hand on a steady mouse to do this effectively. Practice makes perfect!
                  First, look at the squares in your GIMP
                  toolbox. There is a Free Select tool in the upper
                  right corner. We want to use this tool first.
                  Click on the tool to activate and we are ready to
                  begin cutting away.
                   
 
 
                   We will
                  need the image of Daniel of course, so load it
                  up. You might want to zoom his image a little so
                  you can see to cut closer. This can be achieved
                  by moving your mouse over the image window to
                  give it focus, then pressing your plus and minus
                  key on the keyboard. Even though the plus symbol
                  is really shift-equals, you can just hit the key
                  unshifted and GIMP will know you want to zoom in.
                  So you can use the plus and minus to get the most
                  comfortable zoom level and resize the window to
                  your preference to keep all of Daniel's image in
                  view. If you have the image window in focus and
                  right-click, a small GIMP menu will popup. There
                  is an option in this menu called View. If you
                  choose View, it will open up a submenu that will
                  give you operations such as Zoom-In and Zoom-Out,
                  but there is also a menu under the Zoom option
                  that will allow you to choose the exact ratio of
                  the zoom. I chose the 1:2 option to do my
                  selecting.
 We will
                  need the image of Daniel of course, so load it
                  up. You might want to zoom his image a little so
                  you can see to cut closer. This can be achieved
                  by moving your mouse over the image window to
                  give it focus, then pressing your plus and minus
                  key on the keyboard. Even though the plus symbol
                  is really shift-equals, you can just hit the key
                  unshifted and GIMP will know you want to zoom in.
                  So you can use the plus and minus to get the most
                  comfortable zoom level and resize the window to
                  your preference to keep all of Daniel's image in
                  view. If you have the image window in focus and
                  right-click, a small GIMP menu will popup. There
                  is an option in this menu called View. If you
                  choose View, it will open up a submenu that will
                  give you operations such as Zoom-In and Zoom-Out,
                  but there is also a menu under the Zoom option
                  that will allow you to choose the exact ratio of
                  the zoom. I chose the 1:2 option to do my
                  selecting.
                   So once we have the preferred magnification and
                  Daniel is completely viewable, we want to begin
                  selecting. This is where we have to have a steady
                  hand. Make sure you have the Free Select tool
                  chosen and hold down your left mouse button and
                  move your cursor around Daniel's outline.
                  Wherever you move the mouse cursor, the border of
                  the selection you are making will be created. As
                  soon as you leave off of the left mouse button,
                  the selection region will be completed. A
                  selection line will be drawn from where you left
                  off the mouse button to the beginning of the
                  region we selected. So go ahead and make the
                  selection by moving the whole way around Daniel's
                  image, outlining his cute little head and pajama
                  outfit, then ending back where you started. When
                  you leave off the button, his entire image should
                  be outlined, and a moving dotted line will show
                  the border of the selection.
                  So once we have the preferred magnification and
                  Daniel is completely viewable, we want to begin
                  selecting. This is where we have to have a steady
                  hand. Make sure you have the Free Select tool
                  chosen and hold down your left mouse button and
                  move your cursor around Daniel's outline.
                  Wherever you move the mouse cursor, the border of
                  the selection you are making will be created. As
                  soon as you leave off of the left mouse button,
                  the selection region will be completed. A
                  selection line will be drawn from where you left
                  off the mouse button to the beginning of the
                  region we selected. So go ahead and make the
                  selection by moving the whole way around Daniel's
                  image, outlining his cute little head and pajama
                  outfit, then ending back where you started. When
                  you leave off the button, his entire image should
                  be outlined, and a moving dotted line will show
                  the border of the selection.
                   From here, the region of the image that is
                  selected includes everything INSIDE the moving
                  dotted line. We want to cut away everything BUT
                  the region inside, so we need to "invert" the
                  selection so that everything but Daniel's image
                  is selected. This is simple. Make sure your mouse
                  is over top of the image region and click on your
                  right mouse button. Choose the Select submenu,
                  then choose the Invert option. Take note that
                  there by the Insert option is a hotkey sequence.
                  Control-I is the hotkey for inverting the
                  selection. Rather than choosing the option from a
                  menu you can just use the hotkey sequence to do
                  the same thing. So do whichever you want to do to
                  get the selection inverted. After you choose to
                  invert, you will see that the dotted moving line
                  is still around Daniel, but there is also a
                  moving dotted line around the parameter of the
                  image. If you dont see one, during the
                  magnification view process it is possible that
                  you may have made the image bigger than the
                  window in which you are viewing the image, so you
                  will have to use the scroll bars to scroll over
                  to the side of the actualy image. Once you have
                  both sets of moving dotted lines, you know that
                  everything between these dotted lines is
                  selected. Hopefully everything between the dotted
                  lines corresponds to all of the image except
                  Daniel.
                  From here, the region of the image that is
                  selected includes everything INSIDE the moving
                  dotted line. We want to cut away everything BUT
                  the region inside, so we need to "invert" the
                  selection so that everything but Daniel's image
                  is selected. This is simple. Make sure your mouse
                  is over top of the image region and click on your
                  right mouse button. Choose the Select submenu,
                  then choose the Invert option. Take note that
                  there by the Insert option is a hotkey sequence.
                  Control-I is the hotkey for inverting the
                  selection. Rather than choosing the option from a
                  menu you can just use the hotkey sequence to do
                  the same thing. So do whichever you want to do to
                  get the selection inverted. After you choose to
                  invert, you will see that the dotted moving line
                  is still around Daniel, but there is also a
                  moving dotted line around the parameter of the
                  image. If you dont see one, during the
                  magnification view process it is possible that
                  you may have made the image bigger than the
                  window in which you are viewing the image, so you
                  will have to use the scroll bars to scroll over
                  to the side of the actualy image. Once you have
                  both sets of moving dotted lines, you know that
                  everything between these dotted lines is
                  selected. Hopefully everything between the dotted
                  lines corresponds to all of the image except
                  Daniel.
                   Once we have the correct selection, which is
                  everything BUT daniel's image, we want to cut it
                  away. Before we do cut away though, we should
                  "feather" the selection so that the border where
                  the cutaway happens is not so chunky and
                  pixelated. By feathering it we will make it
                  smoother. Right click to get our menu, choose the
                  Select submenu and then choose Feather. The
                  hotkey for this is Shift-Control-F. After you do
                  this the Feather Selection dialog box appears and
                  will allow you to choose an amount to feather the
                  selection by. You can experiment around with this
                  amount to see which produces the results you like
                  best. I used 5 for my amount.
                  Once we have the correct selection, which is
                  everything BUT daniel's image, we want to cut it
                  away. Before we do cut away though, we should
                  "feather" the selection so that the border where
                  the cutaway happens is not so chunky and
                  pixelated. By feathering it we will make it
                  smoother. Right click to get our menu, choose the
                  Select submenu and then choose Feather. The
                  hotkey for this is Shift-Control-F. After you do
                  this the Feather Selection dialog box appears and
                  will allow you to choose an amount to feather the
                  selection by. You can experiment around with this
                  amount to see which produces the results you like
                  best. I used 5 for my amount.
                     You wont be able to see the results until we
                    clear the selection away. If you dont like the
                    results after clearing the selection away, you
                    can use the Undo option twice in a row to undo
                    the clearing of the selection then the
                    feathering of the selection. From there you can
                    choose the Feather option over again and choose
                    a new amount to feather by. To actually clear
                    the selction away, you want to go to the menu
                    by right clicking, choose the Edit submenu,
                    then choose Clear. Control-K is the hotkey to
                    clear. If you dont like the results you can go
                    back and play with the feathering amount by
                    going to the menu, choosing the Edit option,
                    and then choosing Undo. The hotkey for Undoing
                    is Conrtol-Z.
                    You wont be able to see the results until we
                    clear the selection away. If you dont like the
                    results after clearing the selection away, you
                    can use the Undo option twice in a row to undo
                    the clearing of the selection then the
                    feathering of the selection. From there you can
                    choose the Feather option over again and choose
                    a new amount to feather by. To actually clear
                    the selction away, you want to go to the menu
                    by right clicking, choose the Edit submenu,
                    then choose Clear. Control-K is the hotkey to
                    clear. If you dont like the results you can go
                    back and play with the feathering amount by
                    going to the menu, choosing the Edit option,
                    and then choosing Undo. The hotkey for Undoing
                    is Conrtol-Z.
                    
After you clear away, you should have an image with a smoothly cutaway image of Daniel. Like I said, you have to have a steady hand to make this work so practice makes perfect.
                   First, we want to load the picture of Daniel. The
                  particular image I have is in JPG format, and
                  Gimp loads JPGs in RGB truecolor format. In the
                  title of the image window it will specify which
                  format the image is in between the parantheses.
                  If it were loaded from some other format, such as
                  GIF, Gimp might load it as an indexed color image
                  so you would have to convert it to RGB for our
                  purposes. To convert from indexed color to RGB,
                  right click on the image window and choose the
                  Image submenu. In this submenu is RGB, Greyscale,
                  and Indexed options. Just choose the format you
                  want to convert it to...for our demo we want RGB.
                  After you click on that option, our image is
                  converted to RGB. Since RGB format is capable of
                  displaying more colors, converting from RGB to
                  indexed and back may reduce the quality of the
                  image. So if you start in RGB format, stay in RGB
                  format if possible.
                  First, we want to load the picture of Daniel. The
                  particular image I have is in JPG format, and
                  Gimp loads JPGs in RGB truecolor format. In the
                  title of the image window it will specify which
                  format the image is in between the parantheses.
                  If it were loaded from some other format, such as
                  GIF, Gimp might load it as an indexed color image
                  so you would have to convert it to RGB for our
                  purposes. To convert from indexed color to RGB,
                  right click on the image window and choose the
                  Image submenu. In this submenu is RGB, Greyscale,
                  and Indexed options. Just choose the format you
                  want to convert it to...for our demo we want RGB.
                  After you click on that option, our image is
                  converted to RGB. Since RGB format is capable of
                  displaying more colors, converting from RGB to
                  indexed and back may reduce the quality of the
                  image. So if you start in RGB format, stay in RGB
                  format if possible.
                   Once
                  we know the image is in RGB format, we're almost
                  ready to do the cutaway. Right click on the image
                  window and choose the Dialog submenu. In that
                  submenu choose the Layers and Channels option
                  (hotkey for this is Control-L). The
                  Layers/Channels dialog box appears and we are
                  ready to begin learning to use it. This dialog
                  box allows us to edit image layers and image
                  channels. For now we will concentrate on
                  layers.
 Once
                  we know the image is in RGB format, we're almost
                  ready to do the cutaway. Right click on the image
                  window and choose the Dialog submenu. In that
                  submenu choose the Layers and Channels option
                  (hotkey for this is Control-L). The
                  Layers/Channels dialog box appears and we are
                  ready to begin learning to use it. This dialog
                  box allows us to edit image layers and image
                  channels. For now we will concentrate on
                  layers.
                   An
                  image can have multiple layers in Gimp and each
                  layer can be edited independantly of one another.
                  Right now you should only see one layer which
                  will have a very small version of the Daniel
                  image. It will have an eyeball icon to the left
                  and the layer title to the right. The layer title
                  will be "Background." The Eyeball icon is there
                  to show us that the layer is currently visible in
                  the image window. If we have multiple layers, we
                  can make some visible and some not by toggling
                  the eyeball icon for that layer on or off. You
                  can toggle by clicking on the icon (or where the
                  icon should be if there is none) but for now,
                  since we are working on only a single layer, this
                  wont work for us. For now we will only be working
                  with one layer, but we will be doing operations
                  on the layer that require this layer dialog
                  box.
 An
                  image can have multiple layers in Gimp and each
                  layer can be edited independantly of one another.
                  Right now you should only see one layer which
                  will have a very small version of the Daniel
                  image. It will have an eyeball icon to the left
                  and the layer title to the right. The layer title
                  will be "Background." The Eyeball icon is there
                  to show us that the layer is currently visible in
                  the image window. If we have multiple layers, we
                  can make some visible and some not by toggling
                  the eyeball icon for that layer on or off. You
                  can toggle by clicking on the icon (or where the
                  icon should be if there is none) but for now,
                  since we are working on only a single layer, this
                  wont work for us. For now we will only be working
                  with one layer, but we will be doing operations
                  on the layer that require this layer dialog
                  box.
                     Right now the image of Daniel should be in
                    RGB format. RGB, of course, stand for
                    Red-Green-Blue. Each pixel in the image has a
                    seperate value for red, green, and blue and
                    these values combined control the color of the
                    corresponding pixel. If you dont already know
                    this, it is advised to try to find a tutorial
                    on color theory. What we need to do is get the
                    image into a format that has one additional
                    value other than red, green, or blue. This
                    additional value is called an "alpha" value.
                    The alpha value, or alpha channel, can be used
                    for many purposes, but for our purposes we will
                    be using it as an "opacity value."
                    Right now the image of Daniel should be in
                    RGB format. RGB, of course, stand for
                    Red-Green-Blue. Each pixel in the image has a
                    seperate value for red, green, and blue and
                    these values combined control the color of the
                    corresponding pixel. If you dont already know
                    this, it is advised to try to find a tutorial
                    on color theory. What we need to do is get the
                    image into a format that has one additional
                    value other than red, green, or blue. This
                    additional value is called an "alpha" value.
                    The alpha value, or alpha channel, can be used
                    for many purposes, but for our purposes we will
                    be using it as an "opacity value."
                    
The more opacity a pixel has, the less you can see through it. If a pixel as zero opacity, you can see completely through it, you cant even see the pixel itself. In the Layers/Channels dialog box you'll find the opacity slidebar, and this controls the opacity for the entire layer. If you slide it to the left, the opacity value goes down and you can see through the image. This opacity value controls to what degree the image can be seen through, or in other words, how transparent the image is. What you can do is create multiple layers in an image and have a layer be semi-transparent. If a layer is semi-transparent, you will be able to see through it to the next layer. This can make for some pretty neat effects, but we wont be using it right now. Also, GIMP shows that part of an image is transparent by showing a grey checkerboarded pattern. You will see what I mean when you begin working with transparency.
Instead of using the opacity slidebar to make the layer transparent, we will only be making part of the image transparent, sepcifcly everything except for the image of Daniel himself. In order to do this, we need to give the the image an alpha channel. To do this, position your mouse cursor overtop of the layer title and right click. This will produce a menu with some options. The option we want to choose is "Add Alpha Channel." After we choose this option, the alpha channel will be added and you will see in the image window's title bar it now says (RGB-alpha).
                   Now we can add a "layer mask" to help us with our
                  cutaway. A layer mask will allow us to effectivly
                  mask out the part of the image that we dont want.
                  We want to mask out everything except Daniel's
                  image. We can add a layer mask by right-clicking
                  on the layer title and choosing the Add Layer
                  Mask option. After choosing this option, you
                  should get an "Add Mask Options" dialog box. This
                  will allow you to choose what value the layer
                  mask will have initially. You might not know what
                  to choose right now and what will produce what
                  effects so just choose White (Full Opacity) for
                  right now.
                  Now we can add a "layer mask" to help us with our
                  cutaway. A layer mask will allow us to effectivly
                  mask out the part of the image that we dont want.
                  We want to mask out everything except Daniel's
                  image. We can add a layer mask by right-clicking
                  on the layer title and choosing the Add Layer
                  Mask option. After choosing this option, you
                  should get an "Add Mask Options" dialog box. This
                  will allow you to choose what value the layer
                  mask will have initially. You might not know what
                  to choose right now and what will produce what
                  effects so just choose White (Full Opacity) for
                  right now.
                   After
                  choosing the initial value from the dialog box
                  and clicking OK, you will see in the
                  Layers/Channels dialog box that a new white image
                  was created and displayed between the original
                  image of Daniel and the layer title. This is the
                  layer mask that we just created. Click on the
                  white layer mask image in the Layers/Channels
                  dialog box to activate it. If nothing happens,
                  try clicking on the layer image right beside it
                  and you should see a white border leave the layer
                  mask image and go to the layer image. This shows
                  that the layer image is now active, and you'll
                  want to click back on the layer mask to activate
                  it.
 After
                  choosing the initial value from the dialog box
                  and clicking OK, you will see in the
                  Layers/Channels dialog box that a new white image
                  was created and displayed between the original
                  image of Daniel and the layer title. This is the
                  layer mask that we just created. Click on the
                  white layer mask image in the Layers/Channels
                  dialog box to activate it. If nothing happens,
                  try clicking on the layer image right beside it
                  and you should see a white border leave the layer
                  mask image and go to the layer image. This shows
                  that the layer image is now active, and you'll
                  want to click back on the layer mask to activate
                  it.
After activating the layer mask, you can draw on it to mask out the layer image. Where you draw on the layer mask with BLACK, the layer image will be made transparent. Where you draw on the mask with WHITE, the image will be made opaque. By using different shades of grey you can make the image semi-transparent. The darker the shade if grey, the more transparent it will become. You may also draw on the layer mask with colors to mask out specific color channels, but we dont need to do that right now. For now we will work with black and white to mask out the image. If you look below you will see in the Layers/Channels dialog box that I'm painting the layer mask black and it is turning the image transparent.
                   
  
                   From
                  here you can use any brushes you want to draw
                  around Daniel's image in black, and it will make
                  the image transparent where you draw on the layer
                  mask. I used the Circle Fuzzy (07) 7x7 brush to
                  draw close against Daniel and then used bigger
                  brushes to clear away the rest. I like this
                  method much better because if I mask out
                  something I didn't want to by accident (because
                  my hand is not so steady) I can just draw back
                  over it with white and the image will reappear.
                  To the right is my finished masking.
 From
                  here you can use any brushes you want to draw
                  around Daniel's image in black, and it will make
                  the image transparent where you draw on the layer
                  mask. I used the Circle Fuzzy (07) 7x7 brush to
                  draw close against Daniel and then used bigger
                  brushes to clear away the rest. I like this
                  method much better because if I mask out
                  something I didn't want to by accident (because
                  my hand is not so steady) I can just draw back
                  over it with white and the image will reappear.
                  To the right is my finished masking.
                   We have our mask now, but we still have to apply
                  it to actually commit the masking to the image.
                  This is done easily with the Apply Layer Mask
                  option in the Layers/Channels dialog box menu.
                  When we choose this option from the menu, the
                  layer mask options dialog box will appear. You
                  can choose to apply the mask or just discard it
                  if we dont want it anymore. We do want it, so we
                  choose apply, and the part of the image that we
                  masked is now made transparent. Now we can create
                  additional layers underneath this layer and they
                  will show through the transparent part of this
                  layer. We can put our background and text in
                  layers underneath this one, but we'll save that
                  for next issue.
                  We have our mask now, but we still have to apply
                  it to actually commit the masking to the image.
                  This is done easily with the Apply Layer Mask
                  option in the Layers/Channels dialog box menu.
                  When we choose this option from the menu, the
                  layer mask options dialog box will appear. You
                  can choose to apply the mask or just discard it
                  if we dont want it anymore. We do want it, so we
                  choose apply, and the part of the image that we
                  masked is now made transparent. Now we can create
                  additional layers underneath this layer and they
                  will show through the transparent part of this
                  layer. We can put our background and text in
                  layers underneath this one, but we'll save that
                  for next issue.
            For more information:
            
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2002-11-02, generated by lfparser version 2.34