Index: src/wp-includes/class-wp-image-editor-gd.php
===================================================================
--- src/wp-includes/class-wp-image-editor-gd.php	(revision 26413)
+++ src/wp-includes/class-wp-image-editor-gd.php	(working copy)
@@ -77,7 +77,7 @@
 	 * @since 3.5.0
 	 * @access protected
 	 *
-	 * @return boolean|\WP_Error
+	 * @return boolean|WP_Error True if loaded successfully; WP_Error on failure.
 	 */
 	public function load() {
 		if ( $this->image )
@@ -86,8 +86,16 @@
 		if ( ! is_file( $this->file ) && ! preg_match( '|^https?://|', $this->file ) )
 			return new WP_Error( 'error_loading_image', __('File doesn&#8217;t exist?'), $this->file );
 
+		/**
+		 * Filter the memory limit allocated for image manipulation.
+		 *
+		 * @since 3.5.0
+		 *
+		 * @param int Maximum memory limit to allocate (default is WP_MAX_MEMORY_LIMIT)
+		 */
 		// Set artificially high because GD uses uncompressed images in memory
 		@ini_set( 'memory_limit', apply_filters( 'image_memory_limit', WP_MAX_MEMORY_LIMIT ) );
+
 		$this->image = @imagecreatefromstring( file_get_contents( $this->file ) );
 
 		if ( ! is_resource( $this->image ) )
@@ -105,7 +113,7 @@
 		$this->update_size( $size[0], $size[1] );
 		$this->mime_type = $size['mime'];
 
-		return true;
+		return $this->set_quality( $this->quality );
 	}
 
 	/**
@@ -361,7 +369,7 @@
 				return new WP_Error( 'image_save_error', __('Image Editor Save Failed') );
 		}
 		elseif ( 'image/jpeg' == $mime_type ) {
-			if ( ! $this->make_image( $filename, 'imagejpeg', array( $image, $filename, apply_filters( 'jpeg_quality', $this->quality, 'image_resize' ) ) ) )
+			if ( ! $this->make_image( $filename, 'imagejpeg', array( $image, $filename, $this->quality ) ) ) 
 				return new WP_Error( 'image_save_error', __('Image Editor Save Failed') );
 		}
 		else {
@@ -373,12 +381,19 @@
 		$perms = $stat['mode'] & 0000666; //same permissions as parent folder, strip off the executable bits
 		@ chmod( $filename, $perms );
 
+		/**
+		 * Filter the name of the saved image file.
+		 *
+		 * @since 2.6.0
+		 *
+		 * @param string $filename Name of the file.
+		 */
 		return array(
-			'path' => $filename,
-			'file' => wp_basename( apply_filters( 'image_make_intermediate_size', $filename ) ),
-			'width' => $this->size['width'],
-			'height' => $this->size['height'],
-			'mime-type'=> $mime_type,
+			'path'      => $filename,
+			'file'      => wp_basename( apply_filters( 'image_make_intermediate_size', $filename ) ),
+			'width'     => $this->size['width'],
+			'height'    => $this->size['height'],
+			'mime-type' => $mime_type,
 		);
 	}
 
Index: src/wp-includes/class-wp-image-editor-imagick.php
===================================================================
--- src/wp-includes/class-wp-image-editor-imagick.php	(revision 26413)
+++ src/wp-includes/class-wp-image-editor-imagick.php	(working copy)
@@ -119,6 +119,7 @@
 		if ( ! is_file( $this->file ) && ! preg_match( '|^https?://|', $this->file ) )
 			return new WP_Error( 'error_loading_image', __('File doesn&#8217;t exist?'), $this->file );
 
+		/** This filter is documented in wp-includes/class-wp-image-editor-imagick.php */ 
 		// Even though Imagick uses less PHP memory than GD, set higher limit for users that have low PHP.ini limits
 		@ini_set( 'memory_limit', apply_filters( 'image_memory_limit', WP_MAX_MEMORY_LIMIT ) );
 
@@ -142,7 +143,7 @@
 		if ( is_wp_error( $updated_size ) )
 				return $updated_size;
 
-		return $this->set_quality();
+		return $this->set_quality( $this->quality );
 	}
 
 	/**
@@ -152,15 +153,19 @@
 	 * @access public
 	 *
 	 * @param int $quality Compression Quality. Range: [1,100]
-	 * @return boolean|WP_Error
+	 * @return boolean|WP_Error True if set successfully; WP_Error on failure.
 	 */
 	public function set_quality( $quality = null ) {
-		if ( !$quality )
+		$quality_result = parent::set_quality( $quality );
+		if ( is_wp_error( $quality_result ) ) {
+			return $quality_result;
+		} else {
 			$quality = $this->quality;
+		}
 
 		try {
-			if( 'image/jpeg' == $this->mime_type ) {
-				$this->image->setImageCompressionQuality( apply_filters( 'jpeg_quality', $quality, 'image_resize' ) );
+			if ( 'image/jpeg' == $this->mime_type ) {
+				$this->image->setImageCompressionQuality( $quality );
 				$this->image->setImageCompression( imagick::COMPRESSION_JPEG );
 			}
 			else {
@@ -171,7 +176,7 @@
 			return new WP_Error( 'image_quality_error', $e->getMessage() );
 		}
 
-		return parent::set_quality( $quality );
+		return true;
 	}
 
 	/**
@@ -447,11 +452,12 @@
 		$perms = $stat['mode'] & 0000666; //same permissions as parent folder, strip off the executable bits
 		@ chmod( $filename, $perms );
 
+		/** This filter is documented in wp-includes/class-wp-image-editor-gd.php */ 
 		return array(
-			'path' => $filename,
-			'file' => wp_basename( apply_filters( 'image_make_intermediate_size', $filename ) ),
-			'width' => $this->size['width'],
-			'height' => $this->size['height'],
+			'path'      => $filename,
+			'file'      => wp_basename( apply_filters( 'image_make_intermediate_size', $filename ) ),
+			'width'     => $this->size['width'],
+			'height'    => $this->size['height'],
 			'mime-type' => $mime_type,
 		);
 	}
Index: src/wp-includes/class-wp-image-editor.php
===================================================================
--- src/wp-includes/class-wp-image-editor.php	(revision 26413)
+++ src/wp-includes/class-wp-image-editor.php	(working copy)
@@ -205,19 +205,45 @@
 	 * @access public
 	 *
 	 * @param int $quality Compression Quality. Range: [1,100]
-	 * @return boolean
+	 * @return boolean|WP_Error True if set successfully; WP_Error on failure.
 	 */
-	public function set_quality( $quality ) {
+	public function set_quality( $quality = null ) {
+		if ( $quality == null ) {
+			$quality = $this->quality;
+		}
+
 		/**
 		 * Filter the default quality setting.
 		 *
 		 * @since 3.5.0
 		 *
-		 * @param int $quality Quality level between 0 (low) and 100 (high).
+		 * @param int $quality Quality level between 1 (low) and 100 (high).
 		 */
-		$this->quality = apply_filters( 'wp_editor_set_quality', $quality );
+		$quality = apply_filters( 'wp_editor_set_quality', $quality, $this->mime_type );
 
-		return ( (bool) $this->quality );
+		/**
+		 * Filter the JPEG quality for backwards compatibilty.
+		 *
+		 * @since 2.5.0
+		 *
+		 * @param int $quality Quality level between 0 (low) and 100 (high) of the JPEG.
+		 * @param string The context of the filter.
+		 */
+		if ( 'image/jpeg' == $this->mime_type ) {
+			$quality = apply_filters( 'jpeg_quality', $quality, 'image_resize' );
+
+			// Allow 0, but squash to 1 due to identical images in GD, and for backwards compatibility.
+			if ( $quality == 0 ) {
+				$quality = 1;
+			}
+		}
+
+		if ( ( $quality >= 1 ) && ( $quality <= 100 ) ){
+			$this->quality = $quality;
+			return true;
+		} else {
+			return new WP_Error( 'invalid_image_quality', __('Attempted to set image quality outside of the range [1,100].') );
+		}
 	}
 
 	/**
