Category: Step by Step Instructions

  • How To Estimate Mosaic Colors Using Photoshop Elements

    Irregular Shapes

    It’s easy to estimate the total area of a rectangular or circular mosaic using our tile estimator, but it can be much more difficult if the shape of the mosaic is irregular. In fact, most of the individual color fields in a mosaic are arranged in irregular shapes, unless you are doing an abstract geometrical pattern.

    How do you estimate the area covered by an individual color when it is arranged in irregular shapes throughout a mosaic design?

    The following is a method using Photoshop Elements.

    Use Digital Images

    If you get the image into the computer, the computer already knows how many pixels are that color and the total number of pixels in the image.

    The trick is to find some way for the computer to tell us this information, and there are probably many image editing software packages that could be used in some way to do it. I used Photoshop Elements because that was what I had installed. I would think GIMP and other freeware imaging packages could be adapted in some way as well.

    This method uses Photoshop’s Magic Extractor to cut out the color field, then turning that color field black and putting it on a white background. In the RBG color mode used by JPEGs, white has a value of 255 and black has a value of 0. If we take an average of the value of all pixels, this weighted average divided by 255 will represent the percent of the image area that is NOT the particular color.

    Photoshop Elements Example

    For this example, we will use a jpeg of Henri Matisse’s painting “The Dance” and find the percent of the total area that is covered by blue.

    Henri Matisse painting “The Dance”

    Tip: When you make your own mosaic designs, don’t use one blue color for an area such as this. Instead, use two or even three blues of the same hue but slightly different in shade and mix them together to create visual interest. Note how Matisse’s bold color fields aren’t completely homogenized, even in this digital copy of low resolution.

    Step 1. Use The Magic Extractor To Clip Out The Color Of Interest

    Use the Magic Extractor in Photoshop Elements to clip out the color.

    Image > Magic Extractor has a + highlighter for marking the color you want to save and a second highlighter for marking all the colors you want to delete. You can use the Preview button to see if you have things marked correctly.

    Note that I used the first highlighter to mark the blue in multiple places to make sure that I marked all the different shades of blue. I also marked it in each separate blue area just to be sure, but this isn’t necessary. When I used the second highlighter, I made sure I marked the grass and the dancers in a way that got all the different colors and shades of colors used for them.

    Magic Extractor results in Photoshop Elements

    Notice how efficiently the Magic Extractor removes the non-blue elements.

    Step 2. Use Filter Tools To Black Out The Color Filter > Adjustments > Threshold

    Under the Filter menu, there is a collection of tools called Adjustments. Use the Threshold tool, and drag the pointer to 255. What this is doing is saying black out all color with RBG values under 255, which is the RBG for pure white.

    Step 3. Save As A JPEG With A White Background.

    Notice that the gridded background is not colored at all, which means the image is now a Photoshop file PSD instead of a JPEG. We need to save it as a JPEG with a white background before we can proceed. However, first you should save this PSD file in case you need to backtrack for whatever reason, and then save it as a JPEG.

    Once you have saved it as a JPEG, close this PSD file and open the newly created JPEG.

    Open the JPEG with a white background  Step 4. Use Filter Tools To Set Every Pixel To The Average Color.

    Now comes the real trick of how to find out how many pixels were in the blue area that we turned to black. Photoshop has a tool that will turn every pixel to the average of all the pixel’s current RBG values. All of our pixels are white (RBG = 255) or black (RBG = 0). The weighted average of all these pixels will be a gray with an RBG somewhere between 0 and 255. The larger the blacked area was before the averaging, the darker the gray will be and the lower the RBG number. The Average tool is found under the Filter menu: Filter > Average or Filter > Blur > Average.

    Filter > Blur > Average Step 5. Use The Color Picker Tool To Find The RBG Value Of The Gray.



    Photoshop’s Color Picker tool is the eyedropper icon. Use it to click the image and then the “Select Foreground Color” square at the bottom of the left toolbar.

    Use Photoshop’s Color Picker tool (eyedropper icon) to click the image and then click the “Select Foreground Color” square. This square is at the bottom of the left toolbar. Once you click the square, the dialog window will pop open and show you the RBG (red blue green) values for this gray. Since it is a gray averaged from pure white and pure black, all the RBG values should be the same number.

    In our example, we see that the RBG value for the gray is 149. If we divide 149 by 255, we get 0.58, which means that 58% of the image’s area is the whited-out non-blue colors. To get the percent of the total area that is blue, we subtract 58% from 100% and get 42%.

    Why this works: If the mosaic was completely whited out, then the RBG number we found using the Color Picker would be 255, the number of white. But some of the mosaic was our blacked-out blue area. Black has an RBG number of 0. When all the white pixels (255) were averaged with the black pixels (0), the number calculated for this average was 149. Dividing 149 by 255 tells us the ratio of white area to total area. Grays with a higher RBG number mean that the amount of white area before averaging was larger.

    So let’s say you were making a 6 ft x 4 ft mosaic interpretation of this Matisse painting. The total area is 6 ft x 4 ft = 24 square feet. The area that is blue is 0.42 x 24 square feet =  10.1 square feet.

    You can find out how many tiles you need to cover that blue area using our tile estimator, which has a table of different tile sizes per square foot based on a standard grout gap.

    Faster and Easier Than It Seems

    Note that you will need to do this for all your colors (you can find the area of the last colors by subtracting the rest from 100%). However, this isn’t very much work. In fact, once you do it a few times, you can do this sort of analysis easily and quickly. Keep in mind that if a color isn’t used anywhere but in small areas like trimming and borders, then it might be difficult to block it out using the Magic Extractor tool, but do you really need a close estimate of something that is only used in 5% of the area? (If so, you need to use a higher resolution pattern, and do the analysis in sections.) Also, you can save that color for last and find it’s area by subtracting all the other color area estimates from 100%.


  • How To Enlarge A Mosaic Pattern Or Drawing Using Only A Ruler

    It is easy to enlarge a mosaic pattern or drawing even if you have no confidence in your ability to draw. All you need is a ruler and a pencil.

    For an example, I will show how to enlarge a back and white copy of a painting of mine from years ago called “Singing Love Song to My Art.”

    Example of mosaic pattern made by drawing a grid on a black and white copy of a painting. Verify Proportions

    The larger surface should have the same proportions as your drawing. You can verify proportions  by dividing the width w by the height h of your surface. If this ratio is the same as w / h for your pattern or drawing, then the two have the same proportion.

    proportion = width w / height h

    In our example, the pattern has a ratio of 0.805.

    = 483 mm / 600 mm

    = 0.805.

    If your surface has extra space in one dimension, you can always center your pattern and have extra background space on either side.

    Draw A Grid On Your Pattern

    Use a ruler to draw a grid on your pattern or drawing. The number of grid lines and the spacing between them can be whatever you want, as long as they are spaced evenly, but I usually use about 10 or 12.

    In my example, I want the grid to be 12 cells high, so that means 11 lines spaced at

    600 mm/12 cell


    50 mm/cell.

    Note how the contents of each cell are very simple, just a line or two, something extremely easy to copy. There is no drawing required. Just a few simple lines and curves that anyone who can write should be able to copy. In fact, drawing the grid on the larger surface requires more thought than copying what is in each cell.

    If your pattern still has too much detail in each cell of the grid, then you need to use a finer grid.Try a grid that is say 20 cells high.

    Draw A Grid On The Larger Surface

    The next step is to draw a grid on the larger surface that has the same number of lines as the grid drawn on the pattern. To do this, you need to calculate how far apart the lines need to be spaced. This is found by calculating a ratio for the pattern:

    height of cell / height

    = 50 / 600

    = 0.0833

    Let’s say you want to draw your pattern on a surface that is 215 inches high. How far apart should the lines be spaced going up the height of the surface? To find this, multiply the height of the surface by the ration you calculated for the pattern:

    215 inches * 0.0833

    = 17.92 inches

    In our example, the width of our cells on the large surface should be the same because we used a square grid.

    Note that a ruler is less useful for drawing the larger grid, but yard sticks and t-squares and larger straight edges can be used in the same way.

    Copy Each Cell

    Now you are ready to copy a few lines or curves from each cell. Anyone who can print their name in neat block letters should be able to do this. If each cell still has too much detail to be copied easily, consider using a finer grid that divides the pattern up into smaller cells.

    JPEGs and Digital Photos

    Note that you don’t have to start with paper copy of a pattern. You can use digital images as your pattern. In my example above, I used a digital photograph of my painting as the starting point. I created a black and white copy of it using Adobe Photoshop Elements and then drew my grid using Microsoft Paint. Instead of measuring the drawing with a ruler, I used its dimensions in pixels, and I turned on the ruler and grid feature of Microsoft Paint to know where to draw my lines. If you hold down the shift key as you draw in Microsoft Paint, the line will be perfectly straight.

  • Improvised Double-Reverse Mosaic Method Using Contact Paper And Clear Packing Tape

    One of our customers Tobin is making an 80 square foot garden courtyard mosaic, the theme being the four elements (water, fire, wind, and earth) with a panel devoted to each element.

    Recently Tobin emailed us some pictures of his work in progress, and I think they are worth showing online and not just because they are strong visually. They are also good how-to illustrations for a double-reverse method of laying up mosaic designs. On top of that, they illustrate a very important concept in making art in general, one that is essential.

    Tobin says he cobbled his method together from different things he saw on our website and in books plus some trial and error and some lessons learned while installing a 12 foot by 4 foot shower mosaic.

    In technical terms, what Tobin is doing could be described as an improvised double-reverse method that uses contact paper and clear packing tape instead of lime putty or clay to temporarily hold the tiles.

    Bird detail in progress for Tobin’s mosaic panel for the Wind Element, which will include the bird and a woman playing a flute in a wind-swept flowing gown. Note that the tile will later be covered in clear packing tape, but for now it is held in place by sticky contact paper.

    Here is what Tobin is doing:

    Semi-translucent contact paper is taped down over the sketch of the mosaic design on a worktable. The contact paper is sticky side up, and the stickiness keeps the tile from moving around as they are placed into position along the outlines of the drawing.

    Once the mosaic design is completely laid out on the sticky contact paper. A layer of clear packing tape is stuck down on the face of the mosaic. The clear packing tape is stickier than the contact paper, so the design lifts right off the contact paper when needed. Before removing the contact paper, Tobin cuts the mosaic into workable sections using a box cutter/utility knife.

    Then Tobin does something different from what I would do at this point in the process. At this point, I would remove the contact paper and press the sheet into the thinset mortar I have spread on my surface. After the mortar hardens for 48 hours, I peel off the clear packing tape and grout my mosaic.

    Instead, Tobin transfers his design yet again by gluing it to a sheet of fiberglass mesh using Weldbond Glue, which is a white PVA adhesive. The reason Tobin is doing the extra step with the mesh is because he is making the individual figures in a convenient and portable way that allows him to focus on the details and then arranging the figures on the mesh to create a final design.

    That sort of collage approach to building up the design from individually rendered figures is a good way to make complicated designs and larger pieces more manageable.

    I often do something similar when I draw up scenes on paper. Without intending to do so, I end up cutting out the figures from the the original drawing and arranging them on a new piece of paper because I didn’t like something in the original drawing (maybe one of the figures was too large or oriented at the wrong angle). Then I lay a new piece of paper on top of this collage and trace enough to make a complete drawing.  The meta point is this: there are ways to work around your limitations in skill or specialized materials or even time.

    I will write more about Tobin’s Mosaic and how his method illustrates an essential concept in making art in my next post.

    Tobin’s Water Element panel, from a Four Elements series of garden mosaics.