On 10/24/2012 09:03 AM, wallisonline wrote:

Hi All,

I am a complete n00b so apologies for the question...

I have myself a picture of my kitcar which I am looking to change the colour of however I want to preview a selection of colours using GIMP to see how they look on the car.

Can anyone point me in the direction of a tutorial of how to "overlay" different colours on the car or advise how I go about doing this? I am not sure how to go about selecting just the body of the car so that I can overlay different colours.

I would prefer to not have to hand paint each colour over the body of the car if it can be helped!

Hey,

What you want to do is create a layer mask that isolates the painted part of the car from the rest of the image. What a mask does, is similar to a stencil: Where the mask is white, the layer's content is visible in the finished image(s). Where the mask is black, the layer is transparent and the one(s) below it are visible in the finished image(s).

I am sure there are good tutorials for beginners out there, but I was not able to find one easily, so I will just describe the process and hope for the best...

First you will need to open your source image in the GIMP, find the Layers dialog, and duplicate your base layer (original) twice, so that your working image becomes a stack of three copies of the same image.

Save the new image in .xcf format, and do Control-s on your keyboard after every major step of the process below, to save your work in case you are interrupted and/or "just in case."

Select the middle layer (left click with mouse on the thumbnail in the Layers dialog), and drag and drop white (or any color) from the color selector tool to the main image window. This will change the middle layer to one solid color. Eventually, all your different colors will go here.

Select the top layer, right click the thumbnail in the Layers dialog and select Add Layer Mask from the menu. Accept the default White mask, which leaves the layer fully visible.

Now comes the painting. Click once on the layer mask thumbnail in the Layers dialog to make sure it is selected, then in the main toolbox, select the paint brush tool and make sure the foreground color in the color picker is black.

In the main image window, start painting over the painted parts of the car with black. Since you are paining on the layer's mask, and making the parts you paint transparent, your result will look like you are paining the car white. That's the layer below showing through. In the process of paining the car, you will learn a bit about how important it is to "zoom in close" for detail work, and you will probably want to start by outlining the car with a small brush. If you hold down the shift key and click on the image, you will draw a straight line from wherever you last applied 'paint' to wherever you click with the mouse: Play "connect the dots" wherever possible to make the painting go faster.

Remember that you can tweak and fine tune your layer mask by paining with white to "bring back" parts were the black "goes over the line."

Once all the painted parts of the car are one flat white outline, you can start changing colors.

Select the base layer in the Layers dialog, and in the image window do Colors > Desaturate. You will not see a change in the image window yet, because the two layers above your base layer are blocking your view.

In the Layers dialog, select the second layer - the one with the mask - and use the drop down menu at the top of the dialog to change its mode to Color. Your black and white car will now be visible in the main image window.

Time to start changing paint colors: Leave the second image layer selected, open the color selector, and pick a color, any color. Drag and drop this into the main image window to replace the white in the second layer and viola, a colored car. If the outline is not perfect enough, go back to the layer mask and paint on it with black and/or white to correct errors.

You can play with the Opacity slider control in the Layers dialog to make the colored layer's effect stronger or weaker. You can use the "Colors > Hue / Saturation" tool's Hue slider to tweak the color of your coloring layer, or drag and drop from the color selector tool to get brand new ones.

When you get a color you like, here's one good way to save it:

On your keyboard do Control-Alt-C. This will copy the visible image to your clipboard, including the effects from all layers. Do Control-V to paste this copy into your image as a new floating layer, and click the New Layer button at the bottom of the Layers dialog to anchor it as a new normal layer.

Drag and drop your new layer from the Layers dialog to the main toolbox and viola, it opens as a new image. Save this image in any convenient format and close it. Back in your Layers dialog, left click the eyeball icon next to the new layer to turn it off, making the layer invisible, and continue on to create your next color.

Repeat as needed.

:o)

Steve

On 10/24/2012 09:03 AM, wallisonline wrote:

Hi All,

I am a complete n00b so apologies for the question...

I have myself a picture of my kitcar which I am looking to change the colour of however I want to preview a selection of colours using GIMP to see how they look on the car.

Can anyone point me in the direction of a tutorial of how to "overlay" different colours on the car or advise how I go about doing this? I am not sure how to go about selecting just the body of the car so that I can overlay different colours.

I would prefer to not have to hand paint each colour over the body of the car if it can be helped!

Hey,

What you want to do is create a layer mask that isolates the painted part of the car from the rest of the image. What a mask does, is similar to a stencil: Where the mask is white, the layer's content is visible in the finished image(s). Where the mask is black, the layer is transparent and the one(s) below it are visible in the finished image(s).

I am sure there are good tutorials for beginners out there, but I was not able to find one easily, so I will just describe the process and hope for the best...

First you will need to open your source image in the GIMP, find the Layers dialog, and duplicate your base layer (original) twice, so that your working image becomes a stack of three copies of the same image.

Save the new image in .xcf format, and do Control-s on your keyboard after every major step of the process below, to save your work in case you are interrupted and/or "just in case."

Select the middle layer (left click with mouse on the thumbnail in the Layers dialog), and drag and drop white (or any color) from the color selector tool to the main image window. This will change the middle layer to one solid color. Eventually, all your different colors will go here.

Select the top layer, right click the thumbnail in the Layers dialog and select Add Layer Mask from the menu. Accept the default White mask, which leaves the layer fully visible.

Now comes the painting. Click once on the layer mask thumbnail in the Layers dialog to make sure it is selected, then in the main toolbox, select the paint brush tool and make sure the foreground color in the color picker is black.

In the main image window, start painting over the painted parts of the car with black. Since you are paining on the layer's mask, and making the parts you paint transparent, your result will look like you are paining the car white. That's the layer below showing through. In the process of paining the car, you will learn a bit about how important it is to "zoom in close" for detail work, and you will probably want to start by outlining the car with a small brush. If you hold down the shift key and click on the image, you will draw a straight line from wherever you last applied 'paint' to wherever you click with the mouse: Play "connect the dots" wherever possible to make the painting go faster.

Remember that you can tweak and fine tune your layer mask by paining with white to "bring back" parts were the black "goes over the line."

Once all the painted parts of the car are one flat white outline, you can start changing colors.

Select the base layer in the Layers dialog, and in the image window do Colors > Desaturate. You will not see a change in the image window yet, because the two layers above your base layer are blocking your view.

In the Layers dialog, select the second layer - the one with the mask - and use the drop down menu at the top of the dialog to change its mode to Color. Your black and white car will now be visible in the main image window.

Time to start changing paint colors: Leave the second image layer selected, open the color selector, and pick a color, any color. Drag and drop this into the main image window to replace the white in the second layer and viola, a colored car. If the outline is not perfect enough, go back to the layer mask and paint on it with black and/or white to correct errors.

You can play with the Opacity slider control in the Layers dialog to make the colored layer's effect stronger or weaker. You can use the "Colors > Hue / Saturation" tool's Hue slider to tweak the color of your coloring layer, or drag and drop from the color selector tool to get brand new ones.

When you get a color you like, here's one good way to save it:

On your keyboard do Control-Alt-C. This will copy the visible image to your clipboard, including the effects from all layers. Do Control-V to paste this copy into your image as a new floating layer, and click the New Layer button at the bottom of the Layers dialog to anchor it as a new normal layer.

Drag and drop your new layer from the Layers dialog to the main toolbox and viola, it opens as a new image. Save this image in any convenient format and close it. Back in your Layers dialog, left click the eyeball icon next to the new layer to turn it off, making the layer invisible, and continue on to create your next color.

Repeat as needed.

:o)

Steve

On Wed, 2012-10-24 at 15:03 +0200, wallisonline wrote:

I have myself a picture of my kitcar which I am looking to change the colour of however I want to preview a selection of colours using GIMP to see how they look on the car.

I'd probably try select by colour first, and/or the fuzzy wand. Investigate the litle slider in tool options for how exact the colour march has to be. If you get the whole car selected, grow the selection by a few pixels and feather it, and then you can go to colours->map->wheel and "rotate colours".

The layer mask solution is a good one but it's fairly sophisticated to start with.

The "Beginning GIMP" book has a lot of really good tutorials, I'd recommend it as an introduction.

Liam

There's several video tutorials on youtube using gimp to change a car color - seems to be a strangely popular thing to do.

Seth

On Wed, Oct 24, 2012 at 8:03 AM, wallisonline wrote:

Hi All,

I am a complete n00b so apologies for the question...

I have myself a picture of my kitcar which I am looking to change the colour of however I want to preview a selection of colours using GIMP to see how they look on the car.

Can anyone point me in the direction of a tutorial of how to "overlay" different colours on the car or advise how I go about doing this? I am not sure how to go about selecting just the body of the car so that I can overlay different colours.

I would prefer to not have to hand paint each colour over the body of the car if it can be helped!

Many thanks

-- wallisonline (via gimpusers.com)
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On 10/24/2012 01:44 PM, Jim Clark wrote:

Wow--

I will save this. Incredibly clear and detailed--I have never rally understood those masks. Still don't, but am sure closer!

Hey Jim,

Glad it makes sense to you! I have saved it and I will probably do an illustrated version for my website sometime soon.

Figuring out how to use layer masks is one of the real "breakthroughs" that make the GIMP a powerful tool. I have been using the GIMP for around 10 years, but I still remember how difficult it was for me to wrap my brain around what masks can do.

You can:

* Make templates that enable you to quickly and easily create lots of different versions of an image, i.e. with different colorization as in the present example, or as frames that smaller images will appear in, etc.

* "Remove" part of a layer, spend a half hour working on the image, then "undo" an error you just found in your removal by painting a little white on the corresponding part of the layer's mask. I almost never use the "Eraser" tool - if you have to go back and undo it, you lose all the work you did after using the Eraser.

* You can "paint with any filter" by applying filters and effects to a copied layer, adding a black mask to make the altered layer vanish, then painting the mask with white to make the changes come back only where you want them in the visible image. (Or vice versa: Paint black on a white mask to wipe away the filter effect where you don't want to see it.) I find this method especially useful when working on portrait shots.

* Isolate under-exposed elements from over-exposed elements in photographs, by making a layer copy and masking out the under- exposed part of the top layer. Then you can adjust the brightness and colors of the bright and dark parts of the picture separately. If the contrast between over- and under-exposed areas is strong enough, you can use the Threshold tool on a throw-away layer to create a nearly perfect mask in seconds, that would have taken a LONG time to paint by hand - some call this "finding the natural mask."

* Use a black/white gradient on a layer mask to give the layer a smooth transition from visible to invisible. This sometimes comes in handy when processing flash photographs, i.e. a line of people on a stage where those at the near end are fully exposed and those at the far end are under-exposed.

... and a whole lot more.

:o)

Steve

saving also...

:)

thanks
dan

On 10/24/12, Steve Kinney wrote:

On 10/24/2012 01:44 PM, Jim Clark wrote:

Wow--

I will save this. Incredibly clear and detailed--I have never rally understood those masks. Still don't, but am sure closer!

Hey Jim,

Glad it makes sense to you! I have saved it and I will probably do an illustrated version for my website sometime soon.

Figuring out how to use layer masks is one of the real "breakthroughs" that make the GIMP a powerful tool. I have been using the GIMP for around 10 years, but I still remember how difficult it was for me to wrap my brain around what masks can do.

You can:

* Make templates that enable you to quickly and easily create lots of different versions of an image, i.e. with different colorization as in the present example, or as frames that smaller images will appear in, etc.

* "Remove" part of a layer, spend a half hour working on the image, then "undo" an error you just found in your removal by painting a little white on the corresponding part of the layer's mask. I almost never use the "Eraser" tool - if you have to go back and undo it, you lose all the work you did after using the Eraser.

* You can "paint with any filter" by applying filters and effects to a copied layer, adding a black mask to make the altered layer vanish, then painting the mask with white to make the changes come back only where you want them in the visible image. (Or vice versa: Paint black on a white mask to wipe away the filter effect where you don't want to see it.) I find this method especially useful when working on portrait shots.

* Isolate under-exposed elements from over-exposed elements in photographs, by making a layer copy and masking out the under- exposed part of the top layer. Then you can adjust the brightness and colors of the bright and dark parts of the picture separately. If the contrast between over- and under-exposed areas is strong enough, you can use the Threshold tool on a throw-away layer to create a nearly perfect mask in seconds, that would have taken a LONG time to paint by hand - some call this "finding the natural mask."

* Use a black/white gradient on a layer mask to give the layer a smooth transition from visible to invisible. This sometimes comes in handy when processing flash photographs, i.e. a line of people on a stage where those at the near end are fully exposed and those at the far end are under-exposed.

... and a whole lot more.

:o)

Steve

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I'd add one suggestion to Steve Kinney's excellent layer mask tutorial:

Once you have the car layer masked off, and you've dropped or painted a new color onto the masked layer, try using layer modes (the option menu in the Layers dialog) on the color layer. When you drop a solid color, it won't look right at first, because it won't have any shading or reflections. Layer modes let you combine a solid color (or gradients, or stripes or other patterns) with the lighting from the original photo so it looks a lot more real.

Color mode is the most obvious, but step through each layer mode in turn (you can use down-arrow once you've clicked on the Mode menu) to compare the effects. Some of the modes, like Difference or Overlay, can give you fancy pearl effects that look great on cars. When I give GIMP talks I almost always demonstrate car colorizing (and I have a section about it in chapter 10 of _Beginning_GIMP_) because the results are so impressive.

...Akkana