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UNDERSTANDING COLOR @romainguy

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UNDERSTANDING COLOR @romainguy

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What is color?

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A visual perception that can be described by hue, brightness and colorfulness

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⚛ ☢ ☀ ♨ 10-16 108 wavelength (m)

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⚛ ☢ ☀ ♨ 10-16 108 wavelength (m) 380 700 nanometers

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0 1 Short Medium Long

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×

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0 1

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☀

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☀ ×

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× ☀ ×

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× ☀ ×

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What is color?

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For developers, a tuple of numbers in a color model with a color space

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RGB CMYK L*a*b*

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RGB

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#ff436d

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255,67,109

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1.0,0.26,0.43

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COLOR SPACE?

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3 primaries

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3 primaries white point

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transfer functions 3 primaries white point

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sRGB AdobeRGB ProPhotoRGB

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Transfer functions?

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sRGB P3 Adobe RGB sRGB

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What you saw is how Android handles color spaces Colors are unmanaged

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Source COLOR MANAGEMENT

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Source Destination COLOR MANAGEMENT

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New in O! Source Destination COLOR MANAGEMENT

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Assign Convert

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When in doubt… sRGB!

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// ARGB in sRGB @ColorInt int c = 0xfff436d;

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// Color instance in sRGB
 Color c = Color.valueOf(1.0f, 0.26f, 0.43f);

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// Color instance in sRGB
 Color c = Color.valueOf(1.0f, 0.26f, 0.43f);

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// Color instance in sRGB
 Color c = Color.valueOf(1.0f, 0.26f, 0.43f); // Color instance in Adobe RGB
 Color c = Color.valueOf(1.0f, 0.26f, 0.43f, 1.0f,
 ColorSpace.get(ColorSpace.Named.ADOBE_RGB));

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// Color instance in sRGB
 Color c = Color.valueOf(1.0f, 0.26f, 0.43f); // Color instance in Adobe RGB
 Color c = Color.valueOf(1.0f, 0.26f, 0.43f, 1.0f,
 ColorSpace.get(ColorSpace.Named.ADOBE_RGB));

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// Color instance in sRGB
 Color c = Color.valueOf(1.0f, 0.26f, 0.43f); // Color instance in Adobe RGB
 Color c = Color.valueOf(1.0f, 0.26f, 0.43f, 1.0f,
 ColorSpace.get(ColorSpace.Named.ADOBE_RGB)); // From Adobe RGB to Display P3
 Color r = c.convert(
 ColorSpace.get(ColorSpace.Named.DISPLAY_P3));

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// RGBA in Adobe RGB
 @ColorLong long c = Color.pack(1.0f, 0.26f, 0.43f, 1.0f,
 ColorSpace.get(ColorSpace.Named.ADOBE_RGB));

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Red, 16 bits Green, 16 bits Blue, 16 bits Alpha, 10 bits Colorspace, 6 bits @ColorLong

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Red, 16 bits Green, 16 bits Blue, 16 bits Alpha, 10 bits Colorspace, 6 bits @ColorLong See android.util.Half

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ColorSpace cs = ColorSpace.get(ColorSpace.Named.ADOBE_RGB);
 cs.isWideGamut(); // Returns true
 cs.getModel(); // Returns ColorSpace.Model.RGB // Cast to ColorSpace.Rgb to get primaries, white point, etc.

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// Use connectors for conversions
 ColorSpace.Connector c = ColorSpace.connect(
 ColorSpace.get(ColorSpace.Named.SRGB),
 ColorSpace.get(ColorSpace.Named.ADOBE_RGB)
 );
 float[] adobeRGB = c.transform(1.0f, 0.26f, 0.43f);

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// Change the white point with chromatic adaptation
 ColorSpace d50 = ColorSpace.adapt(
 ColorSpace.get(ColorSpace.Named.SRGB),
 ColorSpace.ILLUMINANT_D50
 );

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Bitmap b = BitmapFactory.decodeStream(…);
 ColorSpace cs = b.getColorSpace();
 // Most likely, cs.isSrgb() == true

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Bitmap b = BitmapFactory.decodeStream(…);
 ColorSpace cs = b.getColorSpace();
 // Most likely, cs.isSrgb() == true Bitmaps are always in the RGB color model

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BitmapFactory.Options opts = new BitmapFactory.Options();
 // What a silly name opts.inJustDecodeBounds = true;
 
 Bitmap b = BitmapFactory.decodeStream(…, opts);
 ColorSpace cs = opts.outColorSpace;

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BitmapFactory.Options opts = new BitmapFactory.Options();
 // Convert at load time opts.inPreferredColorSpace =
 ColorSpace.get(ColorSpace.Named.SRGB);
 
 Bitmap b = BitmapFactory.decodeStream(…, opts);

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BitmapFactory.Options opts = new BitmapFactory.Options();
 // Convert at load time opts.inPreferredColorSpace =
 ColorSpace.get(ColorSpace.Named.SRGB);
 
 Bitmap b = BitmapFactory.decodeStream(…, opts); 16 bit bitmaps are always in linear extended sRGB

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// Let’s create a wide gamut bitmap Bitmap b = Bitmap.createBitmap(
 1920, 1080,
 Bitmap.Config.ARGB_8888, false,
 ColorSpace.get(ColorSpace.Named.ADOBE_RGB)
 );

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// sRGB out @ColorInt int c = b.getPixel(0, 0); // sRGB in
 b.setPixel(0, 0, 0xfff436d);

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// Preserve color space
 ByteBuffer dst = ByteBuffer.allocate(b.getByteCount());
 b.copyPixelsToBuffer(dst);
 dst.rewind();


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// Preserve color space
 ByteBuffer dst = ByteBuffer.allocate(b.getByteCount());
 b.copyPixelsToBuffer(dst);
 dst.rewind();
 // If the bitmap’s config is RGBA_F16
 // the byte buffer contains half floats
 // See android.util.Half

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sRGB

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non-sRGB sRGB

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[Color Space] [Color space]

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non-sRGB sRGB sRGB No wide gamut support ARGB_8888

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non-sRGB extended sRGB sRGB Wide gamut support RGBA_F16

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Extended sRGB? (scRGB)

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res/*-widecg

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Configuration c = getResources().getConfiguration();
 c.isScreenWideColorGamut();


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Configuration c = getResources().getConfiguration();
 c.isScreenWideColorGamut();
 Display d = view.getDisplay();
 d.isWideColorGamut()

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DON’T PANIC

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DON’T PANIC —— — — — — — —— —

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https://goo.gl/aeJc06 Learn more about transfer functions Starts at minute 29 android.graphics.ColorSpace.Rgb

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https://goo.gl/5w7AQ2 Learn about banding and dithering Starts at minute 36

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Questions