Specify publish settings for PNG files

PNG is the only cross-platform bitmap format that supports transparency (an alpha channel). It is also the native file format for Adobe® Fireworks®.

Flash exports the first frame in the SWF file as a PNG file, unless you mark a different keyframe for export by entering the #Static frame label.

  1. Select File > Publish Settings, click Formats, and select PNG Image.
  2. For the PNG filename, either use the default filename, or enter a new filename with the .png extension.
  3. Click PNG.
    Dimensions
    Enter values for width and height in pixels for the exported bitmap image, or select Match Movie to make the PNG image the same size as the SWF file and maintain the aspect ratio of your original image.

    Bit depth
    Set the number of bits per pixel and colors to use in creating the image. The higher the bit depth, the larger the file.

    • 8-bits per channel (bpc) for a 256-color image

    • 24‑bpc for thousands of colors

    • 24‑bpc with Alpha for thousands of colors with transparency (32 bpc)

  4. To specify appearance settings for the exported PNG, select from the following options:
    Optimize Colors
    Removes any unused colors from a PNG file’s color table, reducing the file size by 1000 to 1500 bytes without affecting image quality but increasing the memory requirements slightly. Has no effect on an adaptive palette.

    Interlace
    Incrementally shows the exported PNG in a browser as it downloads. Lets the user see basic graphic content before the file completely downloads and might download the file faster over a slow network connection. Do not interlace an animated PNG file.

    Smooth
    Applies anti-aliasing to an exported bitmap to produce a higher-quality bitmap image and improve text display quality. However, smoothing might cause a halo of gray pixels to appear around an anti-aliased image placed on a colored background, and it increases the PNG file size. Export an image without smoothing if a halo appears or if you’re placing a PNG transparency on a multicolored background.

    Dither Solids
    Applies dithering to solid colors and gradients.

    Remove Gradients
    (Default is off) Converts all gradient fills in the application to solid colors using the first color in the gradient. Gradients increase the size of a PNG and are often poor quality. To prevent unexpected results, select the first color of your gradients carefully if you use this option.

  5. If you selected 8‑bpc for Bit Depth, select a Dither option to specify how pixels of available colors are mixed to simulate colors not available in the current palette. Dithering can improve color quality, but it increases file size. Select from the following options:
    None
    Turns off dithering and replaces colors not in the basic color table with the solid color from the table that most closely approximates the specified color. Turning dithering off can produce smaller files but unsatisfactory colors.

    Ordered
    Provides good-quality dithering with the smallest increase in file size.

    Diffusion
    Provides the best-quality dithering but increases file size and processing time. It also works only with the Web 216-color palette selected.

  6. Select one of the following Palette Types to define the color palette for the PNG image:
    Web 216
    Uses the standard 216‑color, web-safe palette to create the PNG image, for good image quality and the fastest processing on the server.

    Adaptive
    Analyzes the colors in the image and creates a unique color table for the selected PNG file. Best for systems showing thousands or millions of colors; it creates the most accurate color for the image but results in a file size larger than a PNG created with the web-safe 216-color palette.

    Web Snap Adaptive
    Is the same as the Adaptive palette option except that it converts colors similar to the web-safe 216-color palette. The resulting color palette is optimized for the image, but when possible, Flash uses colors from the web-safe 216-color palette. This produces better colors for the image when the web-safe 216-color palette is active on a 256‑color system. To reduce the size of a PNG file with an adaptive palette, use the Max Colors option to decrease the number of palette colors.

    Custom
    Specifies a palette that you optimized for the selected image. The custom palette is processed at the same speed as the web-safe 216-color palette. To use this option, know how to create and use custom palettes. To select a custom palette, click the Palette folder icon (the folder icon that appears at the end of the Palette text field), and select a palette file. Flash supports palettes saved in the ACT format that leading graphics applications export.

  7. If you selected the Adaptive or Web Snap Adaptive palette, enter a value for Max Colors to set the number of colors used in the PNG image. A smaller number of colors can produce a smaller file but might degrade the colors in the image.
  8. To select a line-by-line filtering method to make the PNG file more compressible and experiment with the different options for a particular image, select one of the following Filter options:
    None
    Turns off filtering.

    Sub
    Transmits the difference between each byte and the value of the corresponding byte of the previous pixel.

    Up
    Transmits the difference between each byte and the value of the corresponding byte of the pixel immediately above.

    Average
    Uses the average of the two neighboring pixels (left and above) to predict the value of a pixel.

    Path
    Computes a simple linear function of the three neighboring pixels (left, above, upper left), and selects the neighboring pixel closest to the computed value as a predictor of the color.

    Adaptive
    Analyzes the colors in the image and creates a unique color table for the selected PNG file. Best for systems showing thousands or millions of colors; it creates the most accurate color for the image but results in a file size larger than a PNG created with the web 216-color palette. Reduce the size of a PNG created with an adaptive palette by decreasing the number of colors in the palette.

  9. Click OK.