CODEWITHSUNDEEP
androidbitmapandroid-bitmap
Roi Amiel
Roi Amiel

Reputation: 365

In what cases BitmapFactory.Options.inPreferredConfig not working?

I'm trying to decode a bitmap from an InputStream using BitmapFactory.decodeStream, and I want to receive the bitmap in ARGB_8888, so I used BitmapFactory.Options.inPreferredConfig = ARGB_8888 but some of my users somehow manage to load a bitmap in a different configuration (RGBA_F16), which makes sense giving the fact that the name of the field is Preferred, But why is that? In what cases Android can't load a bitmap in the inPreferredConfig? the source code is not very clear about that. my solution will be to convert the bitmap to ARGB_8888 using Bitmap.copy, or Canvas.drawBitmap, but before that, I want to understand why it happened. Thanks.

Upvotes: 2

Views: 290

Answers (1)

zyzhang
zyzhang

Reputation: 75

The documentation of BitmapFactory.Options describes the role of inPreferredConfig like this: If this is non-null, the decoder will try to decode into this color space. Although you specify Bitmap.Config.ARGB_8888, it will eventually be adjusted according to the image file itself.

The following code illustrates how the color space of the image is determined:

SkColorType SkAndroidCodec::computeOutputColorType(SkColorType requestedColorType) {
    bool highPrecision = fCodec->getEncodedInfo().bitsPerComponent() > 8;
    switch (requestedColorType) {
        case kARGB_4444_SkColorType:
            return kN32_SkColorType;
        case kN32_SkColorType:
            break;
        case kAlpha_8_SkColorType:
            // Fall through to kGray_8.  Before kGray_8_SkColorType existed,
            // we allowed clients to request kAlpha_8 when they wanted a
            // grayscale decode.
        case kGray_8_SkColorType:
            if (kGray_8_SkColorType == this->getInfo().colorType()) {
                return kGray_8_SkColorType;
            }
            break;
        case kRGB_565_SkColorType:
            if (kOpaque_SkAlphaType == this->getInfo().alphaType()) {
                return kRGB_565_SkColorType;
            }
            break;
        case kRGBA_F16_SkColorType:
            return kRGBA_F16_SkColorType;
        default:
            break;
    }

    // F16 is the Android default for high precision images.
    return highPrecision ? kRGBA_F16_SkColorType : kN32_SkColorType;
}

Upvotes: 1

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