Add ColorImage class

app/src/main/java/chat/rocket/android/app/utils/ColorImage.kt

+package chat.rocket.android.app.utils
+
+import android.graphics.drawable.ColorDrawable
+import android.graphics.drawable.Drawable
+import android.support.annotation.ColorInt
+import android.support.annotation.Nullable
+import android.support.v4.graphics.ColorUtils
+import com.facebook.common.internal.ByteStreams
+import com.facebook.imageformat.ImageFormat
+import com.facebook.imageformat.ImageFormatCheckerUtils
+import com.facebook.imagepipeline.common.ImageDecodeOptions
+import com.facebook.imagepipeline.decoder.ImageDecoder
+import com.facebook.imagepipeline.drawable.DrawableFactory
+import com.facebook.imagepipeline.image.CloseableImage
+import com.facebook.imagepipeline.image.EncodedImage
+import com.facebook.imagepipeline.image.QualityInfo
+import java.io.IOException
+
+/**
+ * Simple decoder that can decode color images that have the following format: <color>#FF5722</color>.
+ *
+ * @see {https://github.com/facebook/fresco/blob/master/samples/showcase/src/main/java/com/facebook/fresco/samples/showcase/imageformat/color/ColorImageExample.java}
+ */
+object ColorImage {
+    // Custom ImageFormat for color images.
+    private val imageFormatColor = ImageFormat("IMAGE_FORMAT_COLOR", "color")
+    // XML color tag that our colors must start with.
+    val colorTag = "<color>"
+
+    /**
+     * Creates a new image format checker for [ColorImage.imageFormatColor].
+     *
+     * @return the image format checker.
+     */
+    fun createFormatChecker(): ImageFormat.FormatChecker = ColorFormatChecker()
+
+    /**
+     * Creates a new decoder that can decode [ColorImage.imageFormatColor] images.
+     *
+     * @return the decoder.
+     */
+    fun createDecoder(): ImageDecoder = ColorDecoder()
+
+    fun createDrawableFactory(): ColorDrawableFactory = ColorDrawableFactory()
+
+    /**
+     * Custom color format checker that verifies that the header of the file corresponds to our [ColorImage.colorTag].
+     */
+    class ColorFormatChecker : ImageFormat.FormatChecker {
+        private val header = ImageFormatCheckerUtils.asciiBytes(colorTag)
+
+        override fun getHeaderSize(): Int {
+            return header.size
+        }
+
+        @Nullable override fun determineFormat(headerBytes: ByteArray, headerSize: Int): ImageFormat? {
+            if (headerSize > getHeaderSize()) {
+                if (ImageFormatCheckerUtils.startsWithPattern(headerBytes, header)) {
+                    return imageFormatColor
+                }
+            }
+            return null
+        }
+    }
+
+    /**
+     * Custom closeable color image that holds a single color int value.
+     */
+    class CloseableColorImage(@field:ColorInt @get:ColorInt val color: Int) : CloseableImage() {
+        private var isClosed = false
+
+        override fun close() {
+            isClosed = true
+        }
+
+        override fun getSizeInBytes(): Int = 0
+
+        override fun isClosed(): Boolean = isClosed
+
+        override fun getWidth(): Int = 0
+
+        override fun getHeight(): Int = 0
+    }
+
+    /**
+     * Decodes a color XML tag: <color>#rrggbb</color>.
+     */
+    class ColorDecoder : ImageDecoder {
+
+        @Nullable override fun decode(encodedImage: EncodedImage, length: Int, qualityInfo: QualityInfo, options: ImageDecodeOptions): CloseableImage? {
+            try {
+                // Read the file as a string
+                val text = String(ByteStreams.toByteArray(encodedImage.inputStream))
+
+                // Check if the string matches "<color>#"
+                if (!text.startsWith(colorTag + "#")) {
+                    return null
+                }
+
+                // Parse the int value between # and <
+                val startIndex = colorTag.length + 1
+                val endIndex = text.lastIndexOf('<')
+                var color = Integer.parseInt(text.substring(startIndex, endIndex), 16)
+
+                // Add the alpha component so that we actually see the color
+                color = ColorUtils.setAlphaComponent(color, 255)
+
+                // Return the CloseableImage
+                return CloseableColorImage(color)
+            } catch (e: IOException) {
+                e.printStackTrace()
+            }
+            // Return nothing if an error occurred
+            return null
+        }
+    }
+
+    /**
+     * Color drawable factory that is able to render a [CloseableColorImage] by creating a new [ColorDrawable] for the given color.
+     */
+    class ColorDrawableFactory : DrawableFactory {
+
+        override fun supportsImageType(image: CloseableImage): Boolean {
+            // We can only handle CloseableColorImages.
+            return image is CloseableColorImage
+        }
+
+        @Nullable override fun createDrawable(image: CloseableImage): Drawable? {
+            // Just return a simple ColorDrawable with the given color value.
+            return ColorDrawable((image as CloseableColorImage).color)
+        }
+    }
+}
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